A generous pinch of salt (optional, but it really does make the flavors pop)
Preheat oven to 350.
To make the cake “crust”: Combine the cake mix, egg, and butter and mix well with an electric mixer. Pat the mixture into the bottom of a lightly greased 13 x 9-inch baking pan.
To make the filling: In a large bowl, beat the cream cheese and pumpkin until smooth. Add the eggs, vanilla, and butter; beat together. Next, add the powdered sugar, cinnamon, nutmeg and salt; mix well. Spread pumpkin mixture over cake batter and bake for approximately 50 minutes.
Do not be tempted to overbake: the cake should still jiggle slightly on the top when it’s done.