In a medium mixing bowl, beat cream cheese, sugar, and lemon or lime gelatin on medium speed until creamy. Add eggs and beat until smooth.
2For lemon layer:
In a large mixing bowl, beat with an electric mixer on low speed the cake mix, butter, and egg until well combined and smooth. Press cake mixture evenly into prepared pan; set aside.
3Preheat oven to 350 degrees F.
Spray 9 by 13-inch baking pan lightly with cooking spray; set aside. Prepare cake layers as directed above. Bake for 40 to 45 minutes or until cake barely start to pull away from sides. Cool completely before cutting into squares.