Preheat oven to 350°F and spray a 9x13-inch baking pan with cooking spray and set aside.
In a large bowl or stand mixer, combined all of the cake ingredients until fully mixed and pour into the prepared pan.
Bake for 30 to 40 minutes or until a toothpick comes clean from the center of the cake. Remove from oven and poke holes in the cake with the handle of a wooden spoon or a skewer.
Heat up the hot fudge in the microwave to soften it, then pour it over the top of the cake and allow it to soak in while the cake cools.
Next, prepare your Peanut Butter Frosting according to the recipe instructions here and then spread it over the top of the fudge covered cake. Decorate as desired and enjoy immediately or store in the fridge.
Notes
Ganache or sweetened condensed milk may also be used instead of hot fudge.