Pre-heat the oven to 350-F degrees and grease a 9-inch by 13-inch cake pan; set aside.
Prepare cake mix, adding 1 egg and 1 stick of melted margarine. Pour the batter into the prepared cake pan, then press down.
Mix the softened cream cheese, remaining 2 eggs, confectioners sugar (reserving enough to dust over finished cake), and remaining stick of melted margarine together in a small mixing bowl. Pour the mixture over the batter in the cake pan.
Bake for 40 to 50 minutes without opening the oven door. When done, the cake will appear very fluffy, but will "deflate" and crack as it cools.
After the cake cools, sprinkle it with a dusting of powdered sugar.