About 5 hours before serving or early in the day, heat vegetable oil in 10" skillet over medium-high heat. Cook sesame seeds in hot oil until golden, stirring grequently. In large zipper lock bag, mix well, sesame seed oil mixture, onions, soy sauce, lemon juice, sugar, pepper and garlic. Trim any excess fat from steak; place steak in marinade, turning to coat both sides. Refrigerate at least 4 hours, turning steak occasionally. About 45 minutes before serving, preheat grill. Grill for 25 minutes for rare. Brush often with marinade; turn steak once.