Pre-heat oven to 350 degrees. In 2 quart casserole, stir together beans, onion, brown sugar, ketchp and mustard. Bake, uncovered, for 1 hour, or until hot and bubbly. Enjoy!
**Microwave Directions: in 2 qt. microwave safe dish, place onion. Cover with plastic wrap, vented, and microwave on high 2 minutes until onion is soft. Add beans, brown sugar, ketchup and mustard: gently mix well. Cover with vented plastic wrap and microwave on high for 6 minutes. Stir. Uncover completely, and continue to microwave on high for a final 6 minutes. Stir well, and serve.