MICROWAVE BAKED-BEANS CASSEROLE

1 lg onion, chopped
1/3 cup packed dark brown sugar
3 Tbs molasses
2 Tbs dry mustard
1/4 cup Ketchup
2 tsp cider vinegar
2 15-19 oz cans sm white beans, drained/rinsed

In 2-qt casserole, cook onion and next 5 ingredients, covered, on HI 5-7 min until onion is tender, stir halfway thru cooking. Add beans; cook, covered, on MED 25-30 min until most of the liquid is absorbed, stir twice during cooking. Let stand, covered, 5 minutes. Makes 4 servings. Variation: Stir in bite-size pieces of frankfurters during last 3 minutes cooking time.