Remove beef from refrigerator 1 hr before roasting.
Preheat oven to 500 deg.
Sprinkle beef with pepper and place on rack in shallow roasting pan.
Roast for 20 min, reduce heat to 400 deg and roast for 15 min for rare.
Remove to heated platter and keep warm.
Drain off all but 1 T fat from roaster and add onion, wine and beef gravy.
Boil on top of stove for about 10 min or until liquid is reduced by 1/4.
Reduce heat, add dissolved cornstarch and stir for 1 min or until sauce is thickened.
Add 2 T butter and mix lightly.
Serve sauce and beef separately.
Brown flour and fat in small saucepan.
Add beef broth.
Cook, stirring, until thick.