As seen at allrecipes.com
3 egg whites
1 (18.25 ounce) packagewhite cake mix
1 1/3 cups water
2 tablespoons canola oil
red, orange, yellow, green, blue and purple paste food coloring
- Preheat an oven to 350 degrees F (175 degrees C). Grease and flour two 8-inch round cake pans.
- Beat the egg whites with an electric mixer until frothy, about 1 minute. Add the cake mix, water, and canola oil; continue beating for 2 minutes on medium speed.
- Divide the cake batter into six separate bowls. Use a toothpick to scoop a dab of food coloring into one bowl of batter and stir; add more food coloring, if necessary, to reach the desired shade. Repeat with the remaining colors and bowls of batter.
- Scoop spoonfuls of batter into the prepared pans, alternating the colors. Use a toothpick to gently swirl the colors for a marbled effect.
- Bake in the preheated oven until a toothpick inserted into the cake comes clean, about 30-35 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack.