Preheat the broiler to 450ºF.
Melt the butter in a skillet over medium heat. Add the cumin, ginger, coriander, cayenne, paprika, sugar, salt and black pepper and stir until well blended and bubbling. Add the vinegar and stir for another 30 seconds. Remove from heat.
Place the fillets, skin side down, on a greased broiler rack. Spoon half of the butter mixture over the fillets and broil 2-inches below the heat for 5 minutes.
Turn the fillets and cover with the remaining butter mixture. Broil for another 3 minutes or until the fish flakes easily with a fork.
