Place roast in a roasting pan; add onions, salt and pepper.
Bake, covered, at 325° for 3 hours and 30 minutes. Cool and cut into thin slices. Place in a large ovenproof container; add Spicy Sauce. Cover and chill 8 hours. Remove from refrigerator, and let stand at room temp. 30 minutes.
Bake at 350° for 45 minutes or until thoroughly heated. Garnish, if desired. Serve with mashed potatoes.
For sauce: Bring all ingredients to a boil in a Dutch oven over medium heat; reduce heat to low, and cook 1 hour. Cool. Discard bay leaf. Yield 7 cups.
Slow-Cooker Method: Cut roast in half, and place in a 5-qt. slow cooker. Stir together ingredients for Spicy Sauce, and por over uncooked roast. Cook at High 9 hours; remove roat. Cool slightly, and cut into thin slices. Return slices to slow cooker, and cook 1 more hour.