Preheat oven to 350. Combine the cake mix, egg, and butter and mix well with an electric mixer. Put the mixture into the bottom of a lightly greased 13 X 9 baking pan. Prepare filling.
In a large bowl, beat the cream cheese until smooth. Add the eggs, vanilla and butter and beat together. Next, add the powdered sugar and mix well. Spread over cake batter and bake for 40 to 50 mins. Make sure not to over bake as the center should be a little gooey.