Roast Beef with Mushroom & Onions

3 large onions , sliced thin 1 (1 lb) can tomato , crushed and drained in a sieve 2 tablespoons olive oil 3 lbs tied boneless beef rib roast, at room[...]

1/8 cup low sodium beef broth 1 teaspoon water 1 medium onion , cut into eighths 1/2 teaspoon Worcestershire sauce 8 ounces very small red potatoes vegetable[...]