Buttercream Rainbow Tutorial

Buttercream Rainbow Tutorial: A step-by-step tutorial for creating the perfect buttercream rainbows.

So many rainbow cakes, so little time! This St. Patrick’s Day inspired cake is probably my favorite I’ve ever done and I’m so excited for you to try out. These darling rainbows are so easy to create and so fun to make.

Getting Started

Here’s what you’ll need:

  • Two 12-inch piping bags (one for the rainbow colors and one for the white clouds)
  • Wilton 1M piping tip
  • Wilton #10 piping tip
  • Six ZipLock bags
  • Seran wrap
  • Six Americolor food gels (I used, Coral, Copper, Gold, Moss, Navy and Violet)

Plan on using about a half batch of my vanilla buttercream (recipe below) for the rainbows and clouds. Divide the frosting into seven bowls. Tint six of the bowls of frosting your rainbow colors and leave one bowl of frosting white for the clouds.

Place each color of frosting into a ZipLock bag and cut a corner off each bag.

Prepping the Piping Bag for Rainbows

On plastic wrap, pipe a line (about 6-inches long) of each color. Make sure the colors line up and touch one another.

Try to create equal amounts of frosting in each line.

After you’ve piped all six colors, take the end of one side of the plastic wrap and begin to lift it up.

Carefully fold the plastic wrap and buttercream to create a circle of colors.

Be gentle as you fold the buttercream over so that you don’t smash the frosting and create uneven lines.

After you’ve wrapped the buttercream, twist one end of the plastic wrap so the buttercream doesn’t come out. On the other end, cut the plastic wrap close to the buttercream. You’ll then place the wrapped buttercream into the piping bag fitted with the Wilton 1M tip.

Piping Rainbows

To create the rainbow, simply pipe a half circle onto a frozen or chilled cake. For best results, place your cake on a tall cake stand and the place the cake stand on your turn table. It will be much easier for you to pipe if you’re as close to eye level with the cake as possible.

After you’ve piped all the rainbows onto the side of the cake, it’s time to pipe the clouds. Place your white frosting into a piping bag fitted with the Wilton #10 tip.

Again, positioning yourself as close to eye level with the cake as possible will make it much easier to pipe onto the side of the cake.

To create the clouds, simple pipe a sideways “s” or squished “m.”

To finish off the cake, grab the rainbow piping bag again and create a braid around the top of the cake. I left about a half inch from the edge of the cake to where I started by rainbow.

To see a video tutorial of the buttercream braid, take a look at my segment on Fox from December, when I used the braid to create a wreath.

And that’s it! Easy peasy, right? Can’t wait to see you give this a try!

Kelly Clarkson Show

More St. Patrick’s Day Inspired Cakes

Vanilla Buttercream

Light and fluffy vanilla buttercream

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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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    1. Yes, I’m actually working on a new post for it this week, but if you need it before I post, use the vanilla cake from my Funfetti Cake (just without the sprinkles).

  1. well this is just amazingly gorgeous and magical! what a lovely treat to gift to a special loved one!

  2. SO BEAUTIFUL!!!!!

    I have a couple of questions:

    1. You say to cut the frosting recipe in half for the rainbows and clouds. Is that half of the recipe is for the cake and half for the rainbows and clouds? Or is it half in addition to what is used for the cake.

    2. How would you prepare in advance best? Freeze the cake layers and do all the frosting the day of? Or prepare the whole cake and freeze? Or freeze the whole frosted cake and do the rainbows the day of? THANKS

    We are dairy free, so I am going to use shortening. What is the function of the whipping cream so I can think of a sub. Is it thickening, or to make the frosting stiffer?

    Sorry for the questions I LOVE YOUR CAKES, SITE and help!!

    1. hi! So you need one full recipe of the frosting for the cake and an extra half of the frosting recipe for the rainbows. I have a dairy free vanilla frosting you can look at that’s really yummy. And you can make the entire cake ahead of time and freeze it. I have a post “how to freeze thaw and transport cakes” that could be helpful

  3. I did! Only downside is the buttercream too sweet. Everyone is happy looking at the design.
    Wish I can upload picture for you to see. Well not as pretty as yours but I DID IT😅

  4. I am planning to make this cake for my daughter’s 6th birthday, we have been admiring it for one year now!! A couple of questions:
    1. She wants chocolate cake, is that weird with vanilla buttercream? Should I colour the frosting in between the layers?
    2. We are expecting about forty people, should I make x3 6” layers? Or use 8”? Or make 2 cakes?
    Thank you!!!! Love love love your cakes!

  5. I just made these cute little rainbows with my daughter. It came out adorable! I didn’t have enough zip locks so I only made red, yellow and blue frosting – the colors blended together to make, well all the colors!

  6. What size cake pans did you make this cake in? And how many layers did you make? I love the size!

  7. My 3 year old daughter was asking for a rainbow cake for her birthday. She saw this one and said this was what she wanted! I rarely bake so I was nervous. But, I was able to follow your instructions and the rainbows turned out great! Thank you!

  8. Is it possible to veganize this recipe by replacing the 2 cups of butter with 1 cup of vegan butter and 1 cup of high ratio shortening (for stability) and using coconut milk creamer in lieu of the cream? Thanks!

  9. I hope you can make a video on how did you piped the rainbow on the side. 😊 is it somehow twisted? 🤔😍 I am thinking of making this one on April. Thank you so much!

  10. Hi! I would love to make this for my niece’s first birthday smashcake next weekend. Could you please tell me what cake recipe of yours you’ve used for this?
    Thanks so much!