Prepare cake as directed on back of box for a 9 x 13 size cake. (To make this a bakery style moist cake, I use melted butter in the place of the oil and I use milk in place of the water.) Make sure eggs and milk are room temperature.
Once cake is out of oven, cool cake completely. Using a large serving fork or a meat fork with large tines, poke lots of holes throughout the cooled cake, making sure to go all the way to the bottom of cake. Set aside.
In a small bowl or a large glass measuring cup (2 cup size works for me), mix the powdered jello with the hot water until the sugar and gelatin have dissolved. Stir in the cold water.
Pour the gelatin mixture all over the top of cake aiming for the holes in the cake also. To setup the jello in the cake, refrigerate for at least 4 hours or overnight.
Remove cake from refrigerator. Spread whipped topping or cool whip evenly over cake.
(to make a homemade version of whipped topping, blend together 16oz of heavy whipping cream and 1/4 cup of powdered or confectioners sugar until stiff peaks form.)
Slice strawberries and garnish top of cake if desired. Enjoy.
Cake should be refrigerated.