Texas Barbecue Beef Sandwiches

Texas Barbecue Beef Sandwiches

1 1/2 cups ketchup
1 medium (1/2 cup) onion, chopped
1/2 cup firmly packed brown sugar
1/4 cup cider or white wine vinegar
1/4 cup Butter
2 teaspoons chili powder
1 teaspoon finely chopped fresh garlic
2 pounds thinly sliced cooked deli roast beef, cut into strips
12 hamburger buns, split
12 (3/4-ounce) slices American Cheese

Stir together all ingredients except beef, hamburger buns and cheese in 2-quart saucepan. Cook over medium heat, stirring occasionally, until mixture comes to a boil. Reduce heat to low. Stir in beef; cook until heated through (15 to 18 minutes).