Rainbow Layer Cake

Directions

1. 1
   Preheat oven to 350 degrees F. Line six 6-inch cake pans with parchment paper.
2. 2
   Beat egg whites with an electric mixer on medium-high speed until foamy, about 2 minutes.
3. 3
   Increase mixer speed to high and continue beating until soft peaks form, about 3 minutes.
4. 4
   Gradually add 1/2 cup of the sugar, continuing to beat until stiff peaks form, about 3 minutes more.
5. 5
   In another large mixing bowl, cream butter and the remaining 1/2 cup of sugar on medium speed until light and fluffy and increased in volume, about 5 minutes.
6. 6
   Add applesauce, vanilla, and eggs and mix on medium speed for 1 minute more.
7. 7
   Sift together flour, baking powder, and salt.
8. 8
   Add to butter mixture and mix on medium speed for 1 minute.
9. 9
   Pour in 3/4 cup water and mix to combine.
10. 10
    Fold in egg whites with a large spatula.
11. 11
    Divide batter evenly among 6 small bowls.
12. 12
    Starting with the lightest color, tint batter with food coloring, whisking in a few drops at a time until the desired intensity is reached.
13. 13
    Pour each of the colored batters into a different parchment-lined cake pan (each should be half full) and bake until a toothpick inserted in the center comes out clean, about 12 to 15 minutes.
14. 14
    Stack layers according to the colors of the rainbow, spreading a thin layer buttercream between each.
15. 15
    Using an offset spatula, frost the whole cake with a thin layer of buttercream.
16. 16
    Place cake on a freezer-safe plate.
17. 17
    Freeze for 15 minutes, or until buttercream is firm.
18. 18
    Remove from freezer and cover cake in sprinkles.
19. 19
    See how to cover a cake in sprinkles.