Melt half the butter in 11 x 9-inch baking pan. Spread around to coat evenly. Then pour melted butter in mixing bowl; add eggs and beat. Add cake mix and blend thoroughly. Batter will be very thick. Spread batter in buttered pan.
Mix together rest of the ingredients (including rest of melted butter) and pour over cake batter. Bake at 325 degrees F for 40 to 45 minutes.
To keep bottom from browning too much, place another cake pan with water in it on lower rack. Bake until sides are firm, middle will still be wiggly.
Cake will rise and then fall in the middle when it is cooled. Sprinkle with powdered sugar.