Tangy BBQ Sauce

This one is Alison's favorite sauce and possibly mine as well.

1 large onion, finely chopped
2 tablespoons butter, melted
2 1/2 cups ketchup
1 cup white vinegar
1 cup water
2/3 cup firmly packed brown sugar
1/4 cup Worcestershire sauce
2 tablespoons cracked black pepper
2 tablespoons chili sauce
1 tablespoon salt

1. Cook onion in butter in a large saucepan over medium heat until tender, stirring often. Add ketchup and remaining ingredients. Bring to a boil; cover, reduce heat and simmer 30 minutes.

Yields 6 cups.