Whisk scallion, soy sauce, vinegar, honey and ginger in a medium bowl until the honey is dissolved.

Place salmon in a sealable plastic bag, add 3 tablespoons of the sauce and refrigerate; let marinate for 15 minutes.

Reserve the remaining sauce.

Preheat broiler. Line a small baking pan with foil and coat with cooking spray. Transfer the salmon to the pan, skinned-side down.

(Discard the marinade.)

Broil the salmon 4 to 6 inches from the heat source until cooked through, 6 to 10 minutes.

Drizzle with the reserved sauce and garnish with sesame seeds.