V8 Barbecue Sauce

1/3 cup minced onion
2 tablespoons butter
2 teaspoons dry mustard
2 cups V8 juice
2/3 cup plain vinegar
1/4 cup molasses
1/2 teaspoon rosemary
1/2 teaspoon thyme
1/4 teaspoon salt

Saute onion in butter until transparent. Add remaining ingredients and simmer for about 10 minutes.