In a mixing bowl, combine yellow cake mix, 1 egg, and 1 stick of melted butter. Mix until well combined and press into the bottom of a greased baking dish.
In another bowl, beat together pumpkin, cream cheese, 3 eggs, vanilla, powdered sugar, cinnamon, nutmeg, and the remaining melted butter until smooth.
Pour the pumpkin mixture over the cake base in the baking dish.
Bake for 50 minutes or until the center is set. Allow to cool before serving.
Notes
For extra flavor, you can add chopped nuts or chocolate chips to the filling.