2 ounces ancho chili peppers
2 cup water
1 cup ketchup
1 cup cider vinegar
1/2 cup Worcestershire Sauce
2 tablespoon paprika
2 tablespoon dry mustard
1 teaspoon freshly ground pepper
1/2 teaspoon black peppercorns
1/4 cup butter
Toast anchos in a large skillet over medium heat, turning once, until they are softened, 4 to 5 minutes.
Transfer anchos to a saucepan, add water, and bring to a boil. Reduce heat and simmer anchos for 5 minutes. Remove from heat, let stand 10 minutes.
Remove anchos, reserving water. Discard seeds and stems. Puree anchos and reserved water in a blender until smooth.
Transfer ancho mixture and remaining ingredients, except lemon and butter, to a saucepan.
Squeeze juice from lemon half into the mixture and add lemon half.
Bring sauce to a boil; reduce heat and gently boil for 30 minutes.
Remove lemon half; stir in butter.
Makes 4 cups.