Ingredients
- vegetable shortening to grease pans
- 3 cups all-purpose flour
- 4 teaspoons baking powder
- 1/2 teaspoon salt
- 2 sticks (1 cup) unsalted butter, room temperature
- 2 1/3 cups sugar
- 5 large egg whites, room temperature
- 2 teaspoons pure vanilla extract
- 1 1/2 cups milk, room temperature
- Red, orange, yellow, green, blue, and purple gel food coloring
- -filling and crumb coat-
- 9 large egg whites
- 1 3/4 cups sugar
- 2 cups (4 sticks) unsalted butter, cut into small pieces, room temperature
- 2 teaspoons pure lemon extract
- -frosting-
- 5 large egg whites
- 1 cup sugar
- 1 cup (2 sticks) unsalted butter, cut into small pieces, room temperature
- 1 teaspoon pure lemon extract
- approximately 1 pound of rainbow sprinkles (for two cakes)
- If making a tiered cake:
- candy sticks to support the top layer
- 8″ cardboard round for the top layer (10″ round optional)
Instructions
- Begin by preparing as many cake pans as you have with a parchment round. I lay the cale pan on the cutting board with the parchment below, and cut around the outside with a knife. Use shortening to grease the pans, under and on top of the parchment.
- Preheat the oven to 350 degrees.
- Sift together all the dry ingredients. Cream the butter and sugar in the mixer fitted with a paddle attachment on medium high speed. Once the mixture is light and fluffy- about 4 minutes- add the egg whites one at a time, on medium low, until combined. Add the vanilla and scrape down the sides of the bowl. With the mixer on low add the flour mixture alternating with the milk in batches, beginning and ending with the flour.
- Divide the batter equally into 6 bowls.
- Whisk coloring into each bowl.
- Each layer should bake 12-15 minutes, or until the sides pull away and a tester comes out clean. Let the cakes cool in the pan for 10 minutes, then invert them onto a cooling rack. Clean out the pans and start the process again with the next colors.
- Make the Frosting-
- In the bowl of the mixer, set over a pan of simmering water, gently heat the egg whites and sugar until the sugar dissolves, whisking pretty constantly. This takes about 10 minutes. You are supposed to use a candy thermometer and wait for the mixture to come to 140ยบ, but I usually just eye ball it. I test to make sure the sugar is completely dissolved by running a bit between my fingers to make sure I feel no sugar grain.
- With the mixer on medium low, add the butter one piece at a time, mixing well after each addition. Remove the whisk and switch to the paddle attachment. With the mixer on medium high, beat until the buttercream comes together. About 5 minutes. Add the lemon extract
- Place the purple layer on a cake stand and top with 1/2 cup of filling.
- Place the blue layer on top and top with 1/2 cup filling.
- Continue until the cake is filled, apply a thin coating of frosting all around and refrigerate for 30 minutes.
- Make the frosting using the same method as filling.
- Forst the cake and cover the outside with sprinkles.
