[courtesy of blogs.babble.com]

Ingredients:
1 box white cake mix made according
     to package instructions
Neon food coloring in pink, yellow,
     green, turquoise, and purple
3 one-pint canning jars
1 can vanilla frosting
Rainbow sprinkles

Directions:
1.)  Preheat oven to 350 degrees.
2.)  Thoroughly wash and dry the inside of each canning jar. Spray the inside of each jar thoroughly with nonstick cooking spray. Set aside.
3.)  Scoop 1/2 cups of cake batter into five small bowls. Tint each bowl of cake batter with the food coloring until very vibrant.
4.)  Spoon 3 tablespoons of the purple batter into the bottom of each jar. Spoon equal amounts of turquoise batter, then green, yellow, and pink.
5.)  Place the jars in a shallow baking dish, add about 1/4″ in water in the baking dish.
6.)  Place the baking dish in the oven and bake for 35-40 minutes.
7.)  Remove jars and allow to cool completely before scooping a small portion from the top of your cake and adding a frosting and sprinkles to the top.