In a bowl, mix the brown sugar in the hot water until dissolved. Pour into a large resealable plastic bag and mix in wine, soy sauce, olive oil, garlic and lemon pepper. Place salmon in the bag, seal and marinate 8 hours or overnight in the refrigerator.
Preheat barbecue for high heat.
Lightly oil the barbecue grate. Reserving marinade, place salmon on the grill and cook 5 to 8 minutes on each side, or until easily flaked with a fork.
Transfer reserved marinade to a pot. Dissolve the cornflour in cold water. Bring the marinade to a boil, and stir in cornflour mixture to thicken. Serve over the salmon or on the side as a dipping sauce.