Grilled Garlic-Marinated Skirt Steak Tacos

If necessary, trim membrane from the steaks by pulling it away in one piece. Place the steaks in a baking dish, rub with the garlic and oil, and let marinate, chilled, for at least 30 minutes and up to 1 day. Prepare a grill or heat a broiler. Season the steaks generously with coarse salt and grill them over glowing coals or direct heat on a gas grill for about 3 minutes on each side for medium-rare. (Alternatively, broil the steaks 3 inches from the heat for about 4 minutes on each side.) Transfer the steaks to a platter and drizzle with lime juice. Let the steaks stand, loosely covered with foil, for 5 minutes. Cut them diagonally across the grain into thin slices. Make tacos with the accompaniments. Accompaniments: Warm corn or flour tortillas, Charred Spring Onions (recipe follows). Charred Spring Onions:20 spring onions or large scallions (about 4 bunches) 1 tablespoon vegetable oil or mild olive oil1/2 teaspoon salt1 lime, halvedPrepare a grill or heat a broiler. Trim the roots and ends from the spring onions, leaving about 8 inches of green stalkIn a large bowl toss the onions with the oil and salt. Grill the onions on the grill, turning them with tongs 3 or 4 times, for 5 to 7 minutes or until softened and lightly charred. If you don't have a grill, broil the onions on a broiler pan about 3 inches from the heat, turning them with tongs 2 or 3 times, for 10 to 12 minutes. Transfer the onions to a platter and squeeze the lime halves over them.