Instructions

For the Strawberry Cake

1. Preheat your oven to 350 degrees F. Spray three 8-inch cake pans with nonstick spray, line the bottoms with parchment paper and spray again. Set aside.
2. In the bowl of an electric mixer fitted with the paddle attachment, combine the cake flour, sugar, Jell-O, lemon zest, baking powder, and salt. Stir to combine.
3. Add the cubed butter, one piece at a time, and 1 cup of buttermilk to the dry ingredients. Beat on medium-low speed until light and fluffy. About 2 minutes. Scrape down the sides of the bowl.
4. In a small mixing bowl, whisk the egg whites and remaining 1/4 cup buttermilk. Add the mixture to the mixing bowl in 3 separate additions, mixing for about 30 seconds and scraping down the sides of the bowl in between each addition. Mix in the vanilla.
5. Divide the batter evenly between the pans (about 15 ounces of batter in each pan) and bake for 20 to 23 minutes.
6. Let cool in the pans for about 10 minutes and then invert onto wire cooling wraps to cool completely. Cakes can be individually wrapped in plastic wrapped and frozen for a week. If you'd like to freeze them longer than one week, wrap each cake layer in tin foil as well. Level the layers before freezing, if needed.

For the Lemon Curd

1. Whisk the sugar, lemon zest, lemon juice and salt in a medium saucepan. Whisk the yolks in a small bowl and then whisk them into the lemon mixture.
2. Cook the mixture over medium heat, whisking constantly, until it's thick like pudding, about 6 to 8 minutes. Remove from the heat and whisk in the butter a few pieces at a time until incorporated.
3. Strain the mixture through a fine-mesh sieve into a small bowl, pushing it through with a rubber spatula. Press plastic wrap directly onto the surface to prevent a skin from forming. Refrigerate until completely set, at least 4 hours and up to 5 days. 

For the Strawberry Cream Cheese Frosting

1. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and cream cheese on medium speed for about 2 minutes.
2. Turn the mixer to low speed and gradually add the powdered sugar, followed by the strawberry emulsion, cream and salt.
3. Turn the mixer to medium-high speed and beat the frosting for about 5 minutes.
4. Before frosting your cake, mix the frosting by hand with a wooden spoon to push out any air pockets. If the frosting feels too soft to frost or pipe, cover it and refrigerate it for about 30 minutes.  

Assembly

1. Spread a dollop of frosting on a cake board or cake plate to hold the first cake layer in place.
2. Place the first cake layer, top side up, on the cake board and pipe a rim of strawberry frosting around the edges to act as a barrier to the lemon curd. Spread half of the lemon curd (about 3/4 cup) on the cake layer.
3. Top with the next cake layer and repeat step 2.
4. Place the third cake layer, top side down, on the second layer of filling. Apply a thin layer of frosting around the entire cake to lock in the crumbs. Freeze the cake for about 10 to 15 minutes to set the crumb coat.
5. If your frosting feels soft at this point, refrigerate it while the crumb coat sets.
6. Continue frosting your cake, making sure to stir the frosting with a wooden spoon to push out any air pockets.
7. If you're not serving within the day, you can freeze the cake in a cake box or container for up to a week - just make sure to remove the cake from the freezer about 6 hours before you plan to serve it.