PLACE cake layers, top-sides up, in 2 clean 9-inch round pans. Pierce cakes with large fork at 1/2-inch intervals.
ADD boiling water to gelatin mix; stir 2 min. until completely dissolved. Carefully pour over cake layers. Refrigerate 3 hours.
BEAT pudding mix and milk in large bowl with whisk 2 min.; stir in COOL WHIP. Dip 1 cake pan in warm water 10 sec.; unmold onto plate. Spread with about 1 cup pudding mixture. Unmold second cake layer; carefully place on first cake layer. Frost top and side of cake with remaining pudding mixture. Refrigerate 1 hour.