Pumpkin Cake

My aunt Carolyn made this for Drea and I on our last trip to California and it is one of my new favorite fall treats.  Best served cold with lots of whipped cream!

1 package angel food cake mix
1 29oz can pumpkin filling
1 1/2 tablespoons pumpkin pie spice
1 cup water

Mix all ingredients together, pour into a 9x13 non-greased baking dish and bake for 40 min at 350 degrees.  Let cool completely before serving, add whipped topping.