Let's Begin!

Cake

• Preheat the oven to 335°F. Then prepare six 8-inch round cake pans with a round piece of parchment paper in the bottom of the pan for easy removal of the cake.
• Combine 8 ounces of the buttermilk and the oil together and set aside.
• Combine the remaining buttermilk, egg whites, and vanilla together, whisk to break up the eggs, and set aside.
• Combine the flour, sugar, baking powder, baking soda, and salt in the bowl of a stand mixer with the paddle attachment. Mix for 10 seconds to combine.
• Add the softened butter to the dry ingredients and mix on low until the mixture resembles coarse sand.
• Add in your milk/oil mixture and let mix until dry ingredients are moistened, then bump up to medium and let mix for 2 full minutes to develop the cake's structure. If you don't let your cake mix on this step your cake could collapse.
• Scrape the sides and bottom of the bowl and then reduce the speed to low. Add in your egg white/milk mixture in three batches, letting the batter mix for 15 seconds between additions. Scrape down the sides again to make sure everything has been incorporated.
• Divide your batter into 6 bowls evenly. Color each bowl with your food colors.
• Bake your layers for 20-24 minutes or until the edges start pulling away from the cake pan. Do not under-bake or the middle of the cake will collapse.
• Let the cakes cool for 10 minutes inside the pan before flipping them out. The cake will shrink a bit and that is normal.
• Freeze your cake layers for 30-60 minutes before trimming your cakes.

Frosting

• Place the butter and cream cheese into a bowl, then beat until smooth. Add half the icing sugar and mix well. Then, add the remaining icing sugar and beat until smooth.

Let's Assemble the Cake!

• Place the violet sponge on a cake board or plate and spread it with a little icing. Then place the blue sponge on top. Continue layering this way, following the colors of the rainbow. Spread a thin layer of icing around the sides of the cake and chill until firm.
• Spread the remaining icing over the top and sides of the cake. Chill until firm.
• Have fun decorating!