You will need:
One box white instant-cake mix (to get pure white coloring)
Red or Pink food coloring
Green food coloring
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1 cup butter (two sticks)
4 cups powdered sugar
2 tsp clear vanilla
Black decorating gel
1/4 cup skim milk
NOTE: Set out butter ahead of time to bring to room temperature.
1. Mix cake batter according to package instructions. Be sure to use the egg whites recipe to keep the cake snow-white.
2. Pour 1 1/2 cake mix in small bowl. Add green food die (dyes vary in intensities, so use your own judgement for the shade of color).
3. Set aside 1-2 Tbsp white batter in case you run out of dye for one color, as it is very difficult to make all cupcakes identical.
4. Dye remaining cake mix pink using a small amount of red food dye or pink dye.
5. Line cupcake tins with 20-24 WHITE liners. (White allows the watermelon effect to be seen through the wrapper).
6. Divide pink batter between the cupcakes.
7. Divide the green batter between the cupcakes, dropping a plop of batter on top of the pink. Then go back and smooth the green layer to the edge using a small spoon, spatula, or finger!
8. Bake at the recommended temperature and for the recommended amount of time, according to the package.
Vanilla Buttercream Frosting:
1 cup butter (two sticks) - room temperature
4 cups powdered sugar
2 tsp clear vanilla
1/4 cup skim milk
Black decorating gel
1. With an electric mixer, cream the butter.
2. Add milk and vanilla.
3. Add powdered sugar and beat, one cup at a time, until smooth.
4. Frost cupcakes and use the black decorating gel
to make 'seeds' for your watermelons.