Preheat oven to 350. Lightly spray a 9×13 pan with non-stick cooking spray. In a mixing bowl, mix together cake mix (reserving one cup for the topping), melted butter and egg. Spread into greased pan. For the filling, mix all ingredients well and pour over crust mixture in pan. For the topping, mix together reserved cake mix, sugar, cinnamon and butter. Mix until crumbly and sprinkle on the pumpkin filling mixture. Bake 1 hour or until a nice inserted in the middle comes out clean. (just poke it with a knife and make sure it comes out clean). Chill and serve with real whipped cream