Mix melted butter with sugar.
Beat in eggs.
Sift flour with baking powder and add alternately with the milk, beginning and ending with the flour.
Spread mixture in a well-buttered 9-inch square pan.
Sprinkle top with brown sugar, dot with butter, and sprinkle with ground cinnamon.
Bake in preheated hot oven (400° F.) for about 30 minutes.
Serve warm, cut into squares.