Rainbow Birthday Cake

Whisk-Kid
Yields: 8 slices

Cake
2 sticks (226 g) butter, room temp
2 ⅓ c (466 g) sugar
5 egg whites, room temp
2 teaspoons vanilla
3 c (375 g) flour
4 tsp baking powder
½ tsp salt
1½  c (355 g) milk, warmed for 30 sec in microwave to bring to room temp
Red, orange, yellow, green, blue and purple GEL food coloring. Liquid will not be vibrant enough! (I used gel and liquid to get the right colors)

Preheat the oven to 350F degrees. Oil and line how ever many 9” cake pans you have (I have three and I just reused them).

Sift together the flour, baking powder and salt. Set aside.

Cream the sugar and butter, then add the egg whites and add them a little at a time. Add the vanilla and mix until fully incorporated. Then, alternating between wet and dry, add the milk and flour mixture in two parts.

Divide the batter amongst 6 bowls and then whisk a fair amount of the appropriate food color into each bowl. Keep in mind that the color of the unbaked batter will be the color of the baked batter. Pour into the pans and bake for 15 minutes each.

When you remove them from the oven, let them rest on the cooling rack, in the pan, for ten minutes. Then flip, cover, and stash them in the fridge to cool quickly.

Frosting
(I was just winging it so this may or may not work for you, it's pretty basic anyway)
8 oz chocolate
1 cup heavy whipping cream
3-5 Tbsp confectioner's sugar

Melt the chocolate in a double boiler or in the microwave. If using the microwave, melt in 15 second increments to avoid overheating the chocolate.

Whip cream until stiff, adding chocolate to taste.