Trim the outer fat from the steak (or ask the butcher to do so). Rub the fat with the cut lemon to prevent burning and smoking. Score both sides of the tail of the steak and then fold it back towards the main body and attach it to the meat with a small metal skewer or sturdy wooden skewer. (If using a wooden skewer, soak it in water for about 20 minutes first).
Combine the olive oil, garlic, scallions, salt and pepper in a glass or ceramic dish. Put the steak in the dish and turn several times to coat. Cover and marinate at room temperature for 1 hour or in the refrigerator for as long as 4 hours. Turn the meat once or twice during marinating.
Prepare a charcoal or gas grill. Lightly spray the grill rack with vegetable oil cooking spray. The coals should be moderately hot to hot. Lift the steak from the marinade. Discard the marinade. Grill the steak, covered, for 10 to 12 minutes. Turn and grill, covered, for 10 to 12 minutes longer for medium-rare, or until it reaches the desired degree of doneness. Let the meat rest for a few minutes before serving.