Preheat the oven to 300°F. Lightly spray a 9x13 inch baking pan with cooking spray and set aside.
In a medium bowl, mix together the cake mix, melted butter and 1 egg until fully combined. Press this mixture into the bottom of the prepared baking pan and set aside.
In a separate bowl, mix together the cream cheese, powdered sugar, cocoa powder and the remaining 2 eggs until smooth. Spread over top of the cake mixture.
Bake in the preheated oven for 40-50 minutes until golden brown, or until the tops and edges begin to crack.