|Place the onion, green pepper and celery in a 5 quart slow cooker. Add the roast. |
In a large bowl, combine tomatoes, broth, ketchup, brown sugar, Worcestershire sauce, mustard, garlic, soy sauce and pepper. Pour over meat. Cover and cook on low for 5-6 hours or until meat is tender.
Remove meat and vegetables, keep warm.
Skim off fat from cooking juices if necessary, transfer to a small saucepan.
In a small bowl, combine cornstarch and cold water until smooth; stir into cooking juices. Bring to a boil; cook for 2 minutes or until thickened. Serve with roast.