Preheat oven to 350 degrees. Grease a 13x9 inch pan with butter or butter-flavored cooking spray.
Melt your first 1/2 cup of butter.
In your mixing bowl, combine cake mix, melted butter, and one egg.
Beat with an electric mixer until you get dough.
Place dough evenly around greased pan...
...and press dough into the bottom of the pan and slightly up sides.
Press dough until it uniformly covers the entire bottom of your pan. Set aside for now.
Melt your next 1/2 cup of butter.
Wipe out your mixing bowl, then beat softened cream cheese until smooth.
Add in egg, vanilla, and butter, beating until smooth.
Carefully add in powdered sugar a little at a time...
...and beat until your batter is all nice and smooth.
Spread batter over crust in pan with a baking spatula, spreading out to the edges of the pan all around and popping any air bubbles.
Bake in your preheated oven for 40 minutes.
Remove from oven and let cool in pan.
Sift powdered sugar over the top of your cake.
Makes about 30 pieces of gooey butter cake!