PLACE each of 2 baked 9-inch round cake layers, top-sides up, in clean 9-inch round baking pans. Pierce cakes with large fork at 1/2-inch intervals.
STIR boiling water into combined 2 pkg. (85 g each) Jell-O Jelly Powder in medium bowl at least 2 min. until completely dissolved. Pour evenly over cake layers. Refrigerate 3 hours.
DIP one of the cake pans in warm water 10 sec.; unmold onto serving plate. Spread with 1 cup of the whipped topping. Unmold second cake layer; carefully place on first cake layer. Frost top and side of cake with remaining 1 cup whipped topping. Refrigerate at least 1 hour. Decorate as desired. Store leftovers in refrigerator.