Texas Barbecue Sauce

2 tbsp. unsalted butter or margarine
1/4 cup minced onion
1 clove (medium) garlic, minced
1-1/2 tsp. chili powder
1/4 tsp. ground cayenne pepper
2 tbsp. brown sugar
2 cups tomato juice
3/4 cup distilled white vinegar
2 tbsp. Worcestershire® sauce
1/2 tsp. mustard powder (mixed with 1 tbsp. water)
1 tsp. minced chipotlè chili in adobo
2 tbsp. dark molasses
1-1/2 tsp. salt
1/4 tsp. ground black pepper

      Heat butter in a small, nonreactive pan over medium heat until foaming.  Add onion and cook, stirring occasionally until softened, about 2 - 3 minutes.  Add garlic, chili powder, cayenne pepper and brown sugar.  Stir constantly until fragrant, about 20 seconds.  Add tomato juice, 1/2 cup vinegar, Worcestershire sauce, mustard, chipotlè, molasses and salt.  Increase heat to high, bring to a simmer, then reduce heat to medium and continue to simmer, stirring occasionally, until sauce is slightly thickened, reduced to 1-1/2 cups, about 30 - 40 minutes.  Once off heat, stir in pepper and remaining 1/4 cup vinegar.  Cool to room temperature before serving.