Braising in tomato sauce guarantees tender, flavorful beef. Trim all fat from roast. Rub dry mustard and salt into the surface of the meat. Place in a lightly greased, oven-proof dish. Top with onion. Combine tomato sauce, vinegar, thyme and pepper. Pour over roast and cover tightly. Bake at 325 F for 3 hours until meat is tender. 3 oz serving 190 calories, 3 protein choices 2 grams carbohydrate, 23 grams protein, 10 grams fat