Watermelon Cake with Lime Curd

Watermelon Cake with Lime Curd – White cake layers doused in a watermelon simple syrup and layered with watermelon buttercream and lime curd.

Watermelon Lime Cake: white cake layers with a watermelon simple syrup, lime curd and watermelon buttercream. #cakebycourtney #cake #cakerecipe #summercakes #cakes #watermeloncake #limecurd


Who else is so ready for summer? Winter went on way too long around here and I’m not okay with it. To take my mind off the icky weather, I’ve been thinking about all the summer-inspired cakes I want to make. The list continues to grow, so before it gets out of control, I decided to get started with this Watermelon Lime Cake.

I’ve had this cake on my mind for a few reasons:

  1. Watermelon is the fruit of the summer (in my opinion, that is – I could eat all day, everyday).
  2. I’ve seen dozens of watermelon cakes around Pinterest but none of them seem to have a watermelon flavor, just the design.
  3. I wanted to do my own version of a watermelon design.

Watermelon Lime Cake: white cake layers with a watermelon simple syrup, lime curd and watermelon buttercream. #cakebycourtney #cake #cakerecipe #summercakes #cakes #watermeloncake #limecurd

Cake Brainstorming

As I thought about the cake, I had a hard time settling for just the watermelon flavor by itself. A flavor pairing was calling out to me. The missing part? Lime curd! I immediately felt like the tartness of the lime would contrast and compliment the watermelon flavor so well.

I immediately got to work, but this cake didn’t come together as quickly as some of my other cakes. The cake layers took me a few tries to nail.

Watermelon Lime Cake: white cake layers with a watermelon simple syrup, lime curd and watermelon buttercream. #cakebycourtney #cake #cakerecipe #summercakes #cakes #watermeloncake #limecurd

Trial and Error

In my first attempt, I used watermelon Jell-O and my white cake recipe for a base. The batter tasted great but the watermelon flavor completely disappeared during baking. In my second attempt, I used the Jell-O mix again and watermelon puree instead of buttermilk as the liquid. Again, the flavor of the batter was great but it baked out again. I thought about using the LorAnns brand of watermelon candy flavoring but after a taste test with my husband and son, we decided it tasted too much like bubble gum. Scratch that idea!

I knew I needed to stick with watermelon Jell-O… but I had to come up with another way for the flavor to stand out more.

Simple Syrup

I decided to think about it some more and after a good night’s rest, I literally woke up at 6 a.m. with the solution in my head. (I must have worked it all out in my dreams! Wish that was the case with more than just my cake problems. Ha!). 

Instead of incorporating the flavor into the batter, I would incorporate the flavor into the cake… after it was baked. The solution? A watermelon simple syrup, made with water, sugar and watermelon Jell-O.

The watermelon simple syrup turned out perfectly, and when added to the baked cake layers, gave me the flavor I was looking for.

I also added watermelon flavor to the buttercream – again, using the Jell-O (the candy flavoring wasn’t right and watermelon puree wouldn’t hold up in a buttercream). I love the flavor of the buttercream, especially paired with the cake layers and lime curd. 

Overall, I’m so happy with how this cake turned out – both the flavor and the design are exactly what I was going for.

My mom was actually in town when I was going through all my testing and had the chance to sample everything along the way, as well as the final product.  She left about a week ago and keeps texting me to tell me how much she loves this cake and how perfectly the flavors go together. (It literally makes me giddy when people can’t forget the way my cakes taste! Best compliment ever!). 

This truly is a memorable cake and so perfect for summer. I hope you love it!

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Watermelon Lime Cake: white cake layers with a watermelon simple syrup, lime curd and watermelon buttercream. #cakebycourtney #cake #cakerecipe #summercakes #cakes #watermeloncake #limecurd

Watermelon Cake with Lime Curd

5 from 5 votes
Tender white cake layers with watermelon simple syrup, watermelon buttercream and lime curd.
Prep Time 3 hrs
Cook Time 20 mins
Total Time 4 hrs 20 mins



  • 3 cups (339 g) cake flour
  • 1 3/4 cups (350 g) granulated sugar
  • 3 1/2 teaspoons  (14 g) baking powder
  • 1 teaspoon (5.6 g) salt
  • 1 cup (226 g) unsalted butter, cut into cubes, room temperature
  • 1 1/4 cup (300 g) buttermilk room temperature
  • 5 egg whites room temperature
  • 1 teaspoon (4.2 g)  clear vanilla extract
  • Pink food gel optional


  • 1/2 cup (118 g)  water
  • 1/2 cup (100 g)  sugar
  • 1- 3 oz. package of watermelon Jell-O


  • 1- 3 oz. package of watermelon Jell-O
  • 3 tablespoons (44.25 g)  water
  • 2 cups (452 g) unsalted butter slightly cold
  • 6 cups (750 g)  powdered sugar measured and then sifted
  • 3 tablespoons (43.3 g)  heavy cream
  • 2 teaspoons (8.4 g) clear vanilla extract
  • Pinch of salt
  • Pink food gel optional


  • 3/4 cup (150 g) granulated sugar
  • 4 teaspoons lime zest
  • 1/2 cup (112 g) fresh lime juice
  • 3 egg yolks and 3 whole eggs
  • 4 tablespoons (56.5 g) cold unsalted butter, cut into cubes
  • Green food gel optional


  • Chocolate chips


  • For the Cake
  • Preheat your oven to 325 degrees F. Prepare four 6-inch or three 8-inch cake pans by spraying each pan with nonstick spray, lining the bottoms with parchment rounds and spraying the pans again. Set aside.
  • In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and the sugar until light and fluffy, about 2 minutes.
  • Add the egg whites, one at a time, mixing well between each addition, followed by the vanilla. Once combined, mix on medium-high for 1 minute. Add a drop of pink food gel and stir to combine.
  • In a medium bowl, combine the flour, the baking powder, and the salt. Whisk to combine.
  • With the mixer on low speed, alternately add the flour mixture with the buttermilk mixture to the butter mixture in your large mixing bowl.
  • Evenly divide the batter into the prepared pans (about 10 to 11 ounces of batter in each of the four 6-inch pans or 15 ounces in each 8-inch pan).
  • Bake the cake layers for 30 to 33 minutes, until a toothpick inserted in the center comes out clean or with only a few crumbs on it. Let cool in the pans for about 10 minutes before inverting onto cooling racks to cool completely .
  • After the cake layers have cooled completely, level each layer with a cake leveler or serrated knife. At this point, you can apply the watermelon simple syrup (directions below) and begin to stack the cake, or after you apply the watermelon simple syrup, wrap each cake layer individually with plastic wrap and freeze for up to a week. If you want to freeze the cake layers longer, add an additional layer of plastic wrap and then tin foil around each cake layer. Allow the cake layers to thaw for about an hour before assembly,


  • In a small sauce pan, combine the sugar and water. Bring the mixture to a boil, stirring occasionally, until the sugar has completely dissolved in the water. Remove from the heat and stir in the watermelon Jell-O, stirring constantly until the Jell-O has dissolved.
  • Allow the mixture to cool slightly before using a pastry brush or squeeze bottle to apply it onto the cake layers.


  • In in a small saucepan, heat the water and Jell-O until Jell-O dissolves and thickens slightly. Let cool to room temperature.
  • In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed for about 2 minutes, until smooth and slightly lighter in color.
  • Turn the mixer to low and gradually add the powdered sugar. Slowly stream in the Jell-O.
  • Once all the powdered and Jell-O are incorporated, add the heavy cream, vanilla and pinch of salt. Turn the mixer to medium-high and beat for about 5 minutes. If the frosting gets too soft from the warm Jell-O syrup, refrigerate for 15 minutes or so. 
  • Save 1 1/2 cups frosting for the center layers and crumb coat of the cake. You don’t need to add food coloring to this portion.
  • Reserve 1/3 cup of the frosting for the dark green, 1/4 cup for the white, and the rest for the darker pink.


  • In a small sauce pan, combine the sugar, lime juice, and lime zest over medium heat. Stir until the sugar is dissolved. Add the egg yolks and whole eggs, stirring while you add them. Continue to stir while the mixture cooks for about 5 to 6 minutes. The mixture will thicken during this time. Remove it from the heat and add the butter. Stir until smooth.
  • Run the curd through a fine mesh sieve. Once cooled, place plastic wrap directly on top of the curd and refrigerate for at least 4 hours.


  • Place the first cake layer, top side up, on a cake board. Cover the cake layer with 1/4 cup frosting and pipe a rim around the edge of the cake. Fill the center of the cake layer with 2 to 3 tablespoons lime curd. 
  • Continue to stack and fill the cake, following step 1, with the second and third cake layer. Place the final cake layer, top side down on top of the last layer of curd. If the cake feels wobbly, place a couple plastic straws in the cake to act as dowels and keep the cake from sliding around as you apply the crumb coat.
  • Using the remaining light pink buttercream you reserved for the filling and crumb coat, apply a thin layer of frosting around the cake to lock in the crumbs and lime curd. Place the cake in the freezer for 10 minutes while you tint the frosting for the watermelon design.
  • I used about 2 drops of mint green Americolor food gel for the dark green and 1 drop for the light green. I then used about 3 drops of watermelon Americolor food gel for the dark pink and kept a little bit of the original frosting color un-tinted for one layer of the piping as well.
  • After the crumb coat is set, pipe three lines of dark green frosting around the bottom of the cake, followed by one line of light green frosting, one line of white frosting and then the rest in dark pink.
  • Using a cake scraper, scrape the frosting around the cake to smooth out the lines. Add chocolate chips to the dark pink frosting for "seeds".
Cuisine Cake
Course Dessert

Courtney Rich

I’m a self-taught baker, obsessed with cake.

I long ago ditched box mixes in pursuit of melt-in-your-mouth, to-die-for flavor combinations, fillings and textures. I believe cake must be decadent, life-changing and worthy of celebration! And I believe anyone should be able to bake that kind of cake – and I’m here to teach you just that!

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Leave a Comment


  1. I’ve been hobby baking for just under a year and I am so inspired by your work! I can’t wait to start trying some of your recipes, I’m trying the caramel cake today! I do a watermelon cake and also found the loranns oil and jello to not be the greatest BUT I did start using watermelon kool aid squirts to flavour and I absolutely LOVE it! Your Instagram page is one I actually look over daily for inspiration, and now your blog! Thank you 🍰
    My Instagram is @cakesontherock

    1. Yeah the oil is not watermelon flavored at all, but I’ve liked the jell-o as a simple syrup. The kool aid idea is awesome too! Thanks so much for following along. xx

  2. Courtney, do I use the entire amount of the simple syrup? And can I use 8 inch pans if that’s what I have? Thx!

    1. No you do not use all of the simple syrup. Just give it a good douse. And you can do three 8″ layers if you want too and use a little more of the syrup.

  3. I live up in Canada and can’t find watermelon jello. Is there something else I could use so it still tastes like watermelon?

  4. If I made this a day in advance, how would you recommend storing it? Or would it be best to make the day of an evening party?

    1. Day of is always best but you can make ahead of time and keep it in the freezer. Just fully wrap it in saran!

  5. 5 stars
    I ADORE this cake! We had family over and it was a big hit! 5 stars for sure! But there was just one problem. The buttercream wasn’t as thick as we hoped. Slowly it did run down the sides so we had to keep freezing the cake. Do you know what to add to make it more thick but not as sugary?
    I love all of your cakes and can’t wait to see which ones you make in the future!

  6. 4 stars
    I love Cake by Courtney’s recipes! It could be just the jello I used, but the frosting and simple syrup were too much like candy for my preference. Still good and a very clever idea, but not quite my taste. Maybe next time I’d use less jello in the frosting, but watermelon is definitely a tricky flavor since it’s so mild. Fun to try! The curd was delicious and the cake was great. Very summer-y.

  7. 4 stars
    Tasted great but I had to forgo the simple syrup as it immediately turned into a blob of gel. What did I do wrong?? I followed the steps exactly!

  8. 5 stars
    I am planning to make this for my daughter’s 1st birthday. Can you use 3 9inch” plans or is the 8″ or 6″ better? Also thinking of making the cake the day before. Fosting and making curd/assemble day of. Do you think that would be okay? TIA