In a small saucepan heat olive oil over medium-low heat. Cook and stir garlic in hot oil for 1 to 2 minutes or until garlic is lightly golden. Transfer garlic to a blender container. Add lemon juice, Worcestershire sauce, mustard, water, and pepper. Cover; blend until combined. Reserve 2 tablespoons of garlic mixture; set aside. Add yogurt to remaining garlic mixture in blender. Cover and blend until smooth. Chill until serving time.
Thaw salmon, if frozen. Rinse salmon; pat dry. Brush the reserved garlic mixture evenly over salmon. Cover and chill for 30 minutes.
Spray the unheated rack of a broiler pan with nonstick coating. Place the salmon on the rack. Broil 4 to 5 inches from heat for 8 to 12 minutes or until salmon flakes easily when tested with a fork, turning once.
Meanwhile, in a large bowl toss romaine, onion, and Parmesan cheese with the chilled yogurt mixture. Divide romaine mixture among 4 salad plates. Place one salmon fillet on each salad. Top with tomatoes and, if desired, olives. Makes 4 servings.