1) Put oven rack in middle position.
2) Preheat oven to 400°F.
3) Pat meat dry.
4) Stir together allspice,2tsps salt and 1 teaspoon pepper in a small bowl and rub all over meat.
5) Spread half of onions and half of garlic in a 13- by 9-inch roasting pan and arrange meat on top.
6) Spread remaining onions and garlic over meat.
7) Tightly cover pan with foil and roast.
8) Turn meat over after 1 hour, until meat is very tender, about 2 1/2 hours total.
9) Skim fat from pan juices.
10)Slice meat across the grain and sprinkle with parsley.
11)Serve with onions and pan juices.

Chef's Note & Story

Beef can be braised 2 days ahead. Cool meat in juices, uncovered, then slice and chill in juices, covered. Reheat, covered, in a 350°F oven 30 to 40 minutes.