Preheat oven to 350 degrees. Lightly grease a 9 x13-inch baking pan.
CAKE: In a large bowl combine cake mix, egg, and melted butter, mix well with an electric mixer. Pat the mixture into the bottom of prepared baking pan.
FILLING: In a large bowl, beat the cream cheese and pumpkin until smooth. Add eggs, vanilla, and butter, beat together. Slowly add the confectioners' sugar, cinnamon and nutmeg, mix well. Spread pumpkin mixture over cake batter
Bake for 40 to 50 minutes. Make sure not to over bake as the center should be a little gooey. Remove from oven and allow to cool completely before cutting into squares. Serve with fresh whipped cream if desired.