1. In a screw-top jar combine the lime peel, lime juice, 3 tablespoons water, and olive oil. Cover and shake well. Pour half of the lime juice mixture into a small bowl; stir in onion and garlic. Reserve remaining lime juice mixture.
2. Score the beef by making shallow diagonal cuts at 1-inch intervals in a diamond pattern. Repeat on other side. Place beef in a plastic bag set in a shallow dish. Pour the lime juice mixture over the beef. Close bag. Marinate in the refrigerator for 24 hours, turning occasionally.
3. For dressing, in a small bowl gradually stir 3 tablespoons water into fruit pectin; stir in reserved lime juice mixture and honey. Cover and chill for 24 hours.
4. Drain beef, discarding marinade. Grill beef on the rack of an uncovered grill directly over medium coals to desired doneness, turning once. Allow 12 to 14 minutes for medium. (Or, place beef on the unheated rack of a broiler pan. Broil 3 to 4 inches from the heat to desired doneness, turning once. Allow 12 to 14 minutes for medium.)
5. To serve, thinly slice beef across grain. Arrange the greens, tomatoes, and, if desired, the avocado on 4 salad plates. Top with beef. Drizzle each serving with about 2 tablespoons of the dressing. Makes 4 servings.