Preheat oven to 350 °F. Grease a 13x9-inch baking dish.
In a large bowl, combine the cake mix, 1 egg, and ½ cup of melted butter. Mix well with an electric mixer. This will make a crumbly dough-like mixture.
Add the cake mixture to the greased 13x9 inch baking pan. Use your hands to cover the bottom of the pan evenly.
Add the cream cheese to a separate large bowl. Beat with mixer until smooth. Add the remaining 2 eggs, vanilla, and ½ cup of melted butter and beat together.
Add the powdered sugar and continue mixing until smooth.
Spoon the cream cheese mixture over the top of the cake batter, making sure to cover it completely.
Place the baking pan in the oven and bake for 40 to 50 minutes. Do not overbake. The center should be a little gooey.
Remove from the oven and let cool completely before cutting and serving.