Grease a 9-inch square baking pan (or something similar) with butter or coat with non-stick spray. Spread batter into pan. Sprinkle batter with remaining tablespoon of sugar. Bake for 35 minutes, then check for doneness by touching the top gently or by inserting a toothpick. If necessary, return pan to oven, check every five minutes or so — (Note: Baking for as long as 50 minutes might be necessary, especially if you made the batter in advance.) Let cool at least 15 minutes before serving.