Cooking "al carbon"--grilling over charcoal--is a great specialty of northern Mexico. One of the best ways to appreciate their cooking technique is in tacos al carbon, for which the meat, after being marinated and grilled, is coarsely diced and then folded into warmed corn tortillas along with guacamole, salsa, and a grilled green onion-the standard edible garnish for this dish.

Beef Tacos al Carbon

1/2 cup fresh lime juice
3 tablespoons olive oil plus additional oil for grilling the green onions
2 garlic cloves, peeled and crushed
1 teaspoon salt
1/2 teaspoon freshly ground black pepper
1 1/2 pounds. flank steak, trimmed of external fat
16 large green onions, trimmed (leave no more than 3-inches of green top)
16 (6-inch) corn tortillas, warmed
Guacamole
Pico de gallo

1. In a shallow nonreactive dish, stir together the lime juice, 3 tablespoons olive oil, garlic, salt, and freshly ground pepper. Add the flank steak and let it stand at room temperature, covered, turning it once or twice, for 4 hours.
2. Preheat a gas grill (medium high) or light a charcoal fire and let it burn down until the coals are evenly white. Adjust the rack to 6-inches above the heat source. Lay the flank steak on the rack and grill it, covered, turning the steak once, for a total of about 12 minutes for medium-rare, or until done to your liking. Transfer the steak to a cutting board, tent it with foil, and let stand for 10 minutes.
3. Brush the green onions lightly with olive oil and lay them on the grill rack. Cover and cook, turning them once, until they are just lightly browned and becoming tender, a total of 3 or 4 minutes. Transfer them to a platter.
4. Carve the flank steak across the grain and at a slight angle into 1/2-inch slices. Cut the slices crosswise into 1/2-inch cubes. Serve immediately, accompanied by the grilled onions, tortillas, guacamole and salsa.

Makes 16 tacos.