Mom's Baked Beans

1 large can B & M or Bush's Boston-Style Baked Beans
1 T mustard
3 T brown sugar
2 T ketchup
1 T dried minced onion (yes, the dried stuff--if you use fresh, it doesn't cook enough and tastes too raw and onion-y)

Combine in a baking dish; cover tightly and cook at 350˚ for at least 30 minutes.