Place fish in a non-reactive dish. Cover fish with lime juice and sprinkle with salt. Let marinate for 20 minutes in the fridge.
Heat the 2 tbsp of butter in a small saucepan and add the Acapulco Marinade. Bring to a boil, lower the heat and cook for 5 minutes. Season to taste with salt. Let cool to room temperature.
Preheat grill. Lightly grease the grill and place fish. Grill for 4-5 minutes, basting with the sauce at least 3 times. Turn fish over, grill for another 3-4 minutes or until fish is cooked.
Serve with tortillas, avocado, cilantro, onion and limes on the side for garnish. Provecho!