Place the orange juice, brown sugar, ketchup, soy sauce, lemon juice, oil, and black pepper in a small bowl; stir well to combine.
Arrange the fish in a single layer in a baking dish. Pour the orange juice mixture over the fillets. Cover and marinate in the refrigerator for 2 hours, turning once.
Remove the fillets from the marinade, reserving the marinade. Pour the marinade into a small saucepan. Bring to a boil; reduce heat, and simmer for 5 minutes. Set half of the marinade aside.
Place fillets on a lightly greased rack in a shallow roasting pan. Broil fillets 6 inches from heat for 10 to 12 minutes, or until the fish flakes easily when tested with a fork, basting occasionally with the marinade.
Transfer fish to a serving platter. Sprinkle the toasted sesame seeds (I toast mine in a skillet while the fish is in the oven) over the fillets, and serve with the reserved marinade.