Preheat oven to 350 degrees F. Line a 13x9" baking pan with foil, extending the sides of the foil over the edges of the pan. Spray the foil liberally with cooking spray and set aside.

In a large bowl, combine the cake mix, ONE (1) stick of the melted butter and 1 egg until a soft dough forms. Batter will be thick. Press into the prepared pan and set aside.

Meanwhile, beat the cream cheese and vanilla in a large bowl together until blended and smooth. Beat in the remaining 1 stick of melted butter and 3 remaining eggs. Lastly, beat in the powdered sugar until combined.

Bake 40-45 minutes or until the top is golden and the center is just about set. Do NOT over bake as these will continue to set up as they cool and are called gooey bars for a reason. Cool completely before cutting into bars, and dust bars with additional powdered sugar if desired. Store bars covered in the fridge.