Thaw the salmon, if frozen. Rinse salmon; pat dry. Spray the unheated rack of a broiler pan with nonstick coating. Place salmon on rack. Broil 4 to 5 inches from heat for 8 to 12 minutes or until the salmon flakes easily when tested with a fork. (Or, spray a grill basket with nonstick coating. Place salmon in basket. Grill salmon on the grill rack of an uncovered grill directly over medium coals for 8 to 12 minutes or until salmon flakes easily with a fork, turning once.)
Meanwhile, for sauce, in a small saucepan combine the cornstarch, salt, and ground red pepper. Gradually stir in the nectar; add honey and 1 tablespoon vinegar. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 2 minutes more. Remove from heat. Cover; keep warm.
In a large bowl toss together the watercress, spinach, or romaine; cucumber; and 1 tablespoon vinegar. Divide among 4 serving plates. To serve, place salmon on watercress mixture and spoon sauce over each serving. Sprinkle with green onions. Makes 4 servings.