Step 1: Preheat your oven according to the cake mix instructions. Prepare your 9-inch cake pans with cooking spray or parchment paper. Mix the cake batter as directed on the package, pour it into the prepared pans, and bake until golden brown and a toothpick inserted comes out clean. Let the cakes cool completely on a wire rack.
Step 2: In a mixing bowl, dissolve the two packages of Jell-O in 2 cups of boiling water. Stir well until completely dissolved. Allow the mixture to cool for a few minutes.
Step 3: Once the cake layers have cooled, place them back in the cake pans. Using a fork or skewer, poke holes all over the tops of the cakes, ensuring they are evenly spaced.
Step 4: Carefully pour the cooled Jell-O mixture over the cakes, making sure it seeps into the holes. Cover the cakes with plastic wrap and refrigerate for at least 4 hours, or overnight for the best results.
Step 5: After the cakes have set, remove them from the refrigerator and gently lift them from the pans. Place one layer on a serving platter and spread a generous amount of Cool Whip on top. Place the second layer on top and frost the top and sides of the cake with the remaining Cool Whip.
Step 6: Feel free to get creative with decorations! You can add fresh fruits, sprinkles, or additional Jell-O cut into small pieces on top. Slice, serve, and enjoy the colorful explosion of flavors with your guests!