Preheat oven to 350F. Mix cake mix, melted butter, 1 teaspoon, vanilla, and 2 eggs with a spoon. Pat into a 13 x 9-inch baking pan. Mix cream cheese, remaining 2 eggs and 1 teaspoon vanilla with an electric mixer. Slowly beat in powdered sugar. Pour over cake layer. Bake 40 to 45 minutes. Let cool.