What fun!! Can also be made into a cake! My daughters birthday is coming up and I think we will change this up a bit for it! Instead of layered rainbow we will do a tie dye effect. Simply add the food colorings after batter has been poured into pans and swirl with a toothpick!! This is simply a white cake, divided into 4 bowls add food color and scoop into cupcake liners one color at a time. The trick is to make the layers even! Practice! Soooo here is the cake recipe I use. Again just divide the batter into as many colors as you like add food coloring scoop into cake pan or cupcakes fill 2/3 full and bake! I was lazy and used a pre-made red frosting )

1 cup white sugar

1/2 cup butter

2 eggs

2 teaspoons vanilla extract

1 1/2 cups all-purpose flour

1 3/4 teaspoons baking powder

1/2 cup milk

Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×9 inch pan or line a muffin pan with paper liners.
In a medium bowl, cream together the sugar and butter. Beat in the eggs, one at a time, then stir in the vanilla. Combine flour and baking powder, add to the creamed mixture and mix well. Finally stir in the milk until batter is smooth. Pour or spoon batter into the prepared pan.
Bake for 30 to 40 minutes in the preheated oven. For cupcakes, bake 20 to 25 minutes. Cake is done when it springs back to the touch