1 In a shallow ceramic or glass dish, spread half of the onions and ginger.
Sprinkle the meat with 1/4 teaspoon each of the salt and pepper and place it on top.
Spread the remaining onions and ginger on top of the meat. (If using ground ginger, sprinkle it on both sides of the beef along with the salt and pepper.) Cover the dish with plastic food wrap and refrigerate for 1 to 3 hours.
2 Preheat the broiler, setting the rack 6 inches from the heat.
Place the steak on a broiler pan.
In a 10 inch nonstick skillet, heat the oil over moderate heat.
Add the onions and ginger and the remaining 1/4 teaspoon each of saltand pepperand saute, stirring occasionally, for8 to 1 0 minutes or until the onions are golden brown.
Stir in the vinegar.
3 Meanwhile, broil the meat to the desired degree of doneness: 5 minutes on each side for medium-rare, 7 minutes for medium, and 9 minutes for well-done.
Transfer the meat to a cutting board and let stand for 5 minutes before cutting it diagonally into thin slices.