PREHEAT oven to 350°F. Prepare cake mix as directed on package. Divide batter between 2 medium bowls. Add 1/2 pkg. dry lime gelatin mix to 1 of the bowls and 1/2 pkg. dry lemon gelatin mix to remaining bowl; mix well. Pour into separate wax paper-lined greased and floured 9-inch round cake pans.
BAKE 28 to 30 minutes or until toothpick inserted in centers comes out clean. Cool 15 minutes; remove from pans. Cool completely on wire racks.
PLACE lime cake layer on serving plate; spread top with 1 cup of the whipped topping. Top with lemon cake layer. Frost top and side of cake with remaining whipped topping. Refrigerate until ready to serve. Store leftover cake in refrigerator.