Rainbow Birthday Cake

Ingredients:

• 6 egg whites (about 2/3 cup) at room temperature
• 1 cup sugar, divided
• 220 g unsalted butter at room temperature
• 3 tablespoons applesauce
• 2 tsp vanilla extract
• 2 whole eggs
• 2 and 1/4 cups cake flour
• 2 tsp baking powder
• A pinch of salt
• 6 different colors of food coloring
• 2 cups buttercream (Jams, jellies, and other fillings will also work)
• 2 cups rainbow sprinkles, nonpareils, and/or pearlescent jelly beans

Preparation:

1. Preheat oven to 175°C. Line 6 6-inch cake pans with parchment paper.
2. Using a mixer on medium-high speed, beat the egg whites until foamy, about 2 minutes. Increase the mixer speed to high and continue beating until soft peaks form, about 3 minutes. Gradually add 1/2 cup of sugar, continuing to beat until stiff peaks form, about 3 more minutes.
3. In another large bowl, beat the butter with the remaining 1/2 cup sugar on medium speed until light and fluffy, about 5 minutes. Add the applesauce, vanilla, and eggs and beat on medium speed for another 1 minute.
4. Sift together the flour, baking powder, and salt. Add to the butter mixture and mix on medium speed for 1 minute until smooth. Pour in 3/4 cup water and mix. Fold in the egg whites with a large spatula.
5. Divide the batter evenly among 6 small bowls. Tint each portion a rainbow color. Pour each colored batter into a parchment-lined cake pan (fill each pan halfway) and bake until a toothpick inserted into the center comes out clean, about 12–15 minutes.
6. Assemble the cake by layering the layers according to the colors of the rainbow, frosting each layer with a small amount of buttercream. Spread the buttercream over the entire cake.
7. Place the cake on a freezer-safe plate. Freeze for 15 minutes or until the frosting is set. Remove from the freezer and sprinkle the cake with colorful sprinkles.