Bake in a 9×13 cake pan the boxed cake mix according to the direction on the box. When it is done, let it cool.
Once it is cool, poke holes in the cake. Mix your 3 oz box of Jello then pour evenly over the cake. Cover it and pop in the fridge to chill.
When you’re ready to frost it, cover the top of the cake in thawed whipped topping.
Serve and enjoy. When you cut the cake into slices it will have the color of the Jello running through it. Beautiful!