Preheat oven to 350 degrees F. Spray a 9x13 pan with high sides with non stick spray.
In a bowl mix cake mix, 1 stick melted butter and 1 egg. Will make a thick dough, this will be your base or crust.
Dump into pan and use hands to press on to bottom so there is an even thick layer across the bottom.
In another bowl mix pumpkin, room temperature cream cheese and vanilla. Beat on low until smooth. Add in 3 eggs and 1 stick of melted butter. Beat again until smooth.
Add powdered sugar and spices, beat in to incorporate again. Pour on to the crust in your pan, spread out evenly.
Bake for 40-50 minutes until pumpkin layer is set and center is no longer wet and gooey.
Remove from oven and place on cooling rack to cool completely. If you want to serve it cold, wait until room temp and put plastic wrap on top of pan and refrigerate for at least 2 hours.
Slice into squares and put whipped cream on top when served.