Rainbow Cake

Gather the ingredients.

Beat the sugar and butter until creamy and whipped, about 10 minutes.

Whisk together the flour, baking powder, and salt in a bowl until completely combined.

Scrape down the sides of the bowl. Add the flour mixture to the butter and sugar mixture and beat until roughly combined.

Scrape down the sides of the bowl. Blend in the milk and vanilla extract, beat for one minute or until combined and smooth.

Beat the egg whites until they form stiff peaks.

Fold the egg whites into the cake batter until combined. Do this gently so as to not deflate all of the egg whites, but also make sure it's totally combined. Scrape down the sides of the bowl.

Split the batter evenly into 8 different small bowls. Whisk the food coloring into each bowl. You will need: red, pink, orange, yellow, green, blue, light blue, and purple. You can skip the pink or light blue if you want to do fewer layers; just split the batter into 6 or 7 bowls. You will need more food coloring than you think to get the right hue. The cake will lighten as it bakes so the color needs to be very saturated to stay vibrant. Add a few drops at a time until you reach your desired tone.

Prepare four round baking pans. You can use 8- or 9-inch cake pans. Grease the entire pan, then dust with flour, shaking off the excess. Cut a round of parchment paper to fit on the bottom of each pan. This ensures that it will come out completely clean.

Pour four of the batters into the four prepared pans. Smooth the top as best as you can. Bake at 360 F for 10 to 15 minutes.

Remove the cakes from the oven, cool in the pan for 2 minutes. Turn them onto a cooling rack to complete cooling. Peel the parchment paper off of the bottom of the cake. Prepare the pans again for the next four colors and repeat with the remaining batters.

Once the cakes have completely cooled (about 20 minutes), trim the tops to ensure even layers.

Cover with plastic wrap and freeze on a flat surface.

When the cakes have been completely frozen, you can start assembling. Make sure you have the cakes in the order. Add the purple layer to a cake board or just right onto your cake plate. Use a dollop of icing under the first layer to help it stick to the cake board or plate.

Add frosting on top of the layer. Do a thick edge so there won't be any gaps when it is stacked. Add another layer of cake and repeat with the icing. Continue until all of the layers have been stacked.

Do a crumb coat of the entire cake. Add more icing to the edges if you have gaps.

Add your final layer of frosting. Smooth or leave swirly. Style the bottom edge of the cake with more frosting if you wish.

Serve and enjoy!