My friend's mom showed me a picture of this cake and I have wanted to make it ever since. It's surprisingly easy to do and just takes an extra few minutes to add dye to the cake mix. You can just put vanilla frosting on if you would like, but I made whipped cream frosting because it looked like clouds to me. :)
1 vanilla cake mix
Red, orange, yellow, green, blue, and purple food dye
Prepare mix as directed on box. (See, I told you this was easy!) Divide the batter into 6 smaller bowls and add food coloring to each. They don't have to be deep in color, just enough to notice the color difference. Pastel is just fine. Grease, line with parchment paper, grease again, and flour 2 round cake pans. Begin with the red batter and pour 1/2 of the batter into each cake round. Pour 1/2 of the orange batter directly on top of the red in each pan, and continue this process throughout all of the colors. Put in a 350 degree oven and bake for 25-30 minutes.
Whipped Cream Frosting
1 cup heavy whipping cream
1 tsp vanilla extract
2 cups powdered sugar
1 Tbs vanilla pudding mix
Whip the cream until soft peaks form, adding the sugar in stages. Add the vanilla and pudding mix and whip until desired consistency is reached. The pudding in this recipe helps hold the normally delicate whipping cream together and makes the frosting more spreadable.