Combine brown sugar, soy sauce, Dijon mustard for broiling glaze. Reserve two tablespoons of glaze, set aside for sauce.
Broil salmon fillets on unheated broiler pan that has been coated with cooking spray for 8-12 minutes, or until fish flakes with fork. Place pan 4 inches from heat. Turn salmon halfway through cooking. Brush with glaze during last 2 to 3 minutes of broiling.
Add rice vinegar to reserved mixture and serve over broiled salmon.