Preheat oven to 350 degrees F.
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 by 9-inch baking pan. Prepare Filling.
Beat cream cheese until smooth. Add eggs and vanilla. Add butter; beat. Add powdered sugar and mix well. Spread over cake mixture. Bake for 40 to 50 minutes. You want the center to be a little gooey, so do not overbake.