Sweet Balsamic Glazed Salmon

Season the salmon with the salt, pepper, garlic and onion. Combine the balsamic vinegar and the agave in a small dish and liberally brush each fillet.
Place the salmon on a greased broiling pan and broil on the highest rack of the oven for 5 minutes. Baste the fish with the remaining vinegar and turn the oven off.
Allow the fish to sit in the warm oven until it is cooked through, 1 to 3 minutes depending on the thickness of the fish. Remove from the oven and brush with remaining vinegar and serve hot.