Simple Jello Poke Cake

1(18 ozs) box cake mix, any flavor
ingredients for mixing cake
1 sm.(4 serv.) box (sugar free) red jello
(any color/flavor is fine)
1 c. boiling water
1/2 c. cold water
1 (8 ozs) container frozen whipped topping, thawed 
How to make it
Mix and bake cake according to box instructions, baking in a 9″ X 13″ baking pan. Cool about 30 minutes. After removing cake from oven, I mix the jello and boiling water, stirring until completely dissolved. Stir in cold water. 
Let stand until ready to use. 
Using a large pronged fork, poke holes evenly over the top of the cooled cake.  Pour jello over cake, filling all the ‘holes’ as you go. Refrigerate 2 hours. 
Frost with whipped topping; garnish with fresh fruit 
(to match your jello flavor, if desired). Store covered in the fridge.