1Add boiling water to gelatin mixes in medium bowl; stir 2 min. until completely dissolved. Add raspberries; stir until thawed. Pour into 9-inch round pan sprayed with cooking spray.
2Arrange cake slices in concentric circles over gelatin, with slices overlapping as necessary to completely cover gelatin.
3Refrigerate 3 hours or until gelatin is firm. Unmold onto plate; top with COOL WHIP.