1 package (18.25 ounce) yellow cake mix
ingredients to prepare cake according to package directions
1 package (4 serving size) lime gelatin
1 package (4 serving size) lemon gelatin
16 ounces frozen whipped topping, thawed

Heat oven to 350°F. Grease and flour two 9 inch round baking pans. Prepare cake mix as directed on package. Divide batter into 2 bowls. Add lime gelatin to one bowl and lemon gelatin to the other. Mix well and pour into prepared baking pans. Bake 28-30 minutes till toothpick inserted in center comes out clean. Cool 15 minutes before removing to racks to cool completely. Place lime layer on serving plate. Spread with 4 ounces whipped topping. Top with lemon layer and frost top and sides with remaining whipped topping. Store in refrigerator till ready to serve.
Nicole's Note
Also can be made in 9x13 pan. Marble batters together by gently swirling with a knife. Can either cut in half horizontally after completely cooling and frost as directed above, or can just put the frosting on the top of the cake. Very good.