Preheat oven to 350°F. In large bowl, combine cake mix, egg, and butter; mix well.

Pat mixture into lightly greased 13x9-inch baking dish.

Wipe out bowl, add cream cheese, and beat until smooth. Mix in eggs and vanilla.

Add butter and beat until incorporated. Slowly add powdered sugar and mix well.

Spread over cake mixture.

Bake 40-50 minutes or until center is still a little gooey. Don't overbake.