Beef Tenderloin Roast With Mushroom Sauce

1 (3 lb) beef tenderloin 1 tablespoon onion , minced 3 tablespoons butter 2 cups mushrooms , sliced 2 tablespoons all-purpose flour 1 cup beef broth 2[...]

1 1/2 lbs large shallots , halved lengthwise, peeled (about 24) 3 tablespoons olive oil 6 cups canned beef broth 1 1/2 cups tawny port 1 tablespoon tomato[...]