Combine the butter, lemon juice, white wine vinegar, lemon peel, garlic salt and salt; stir thoroughly. Generously brush both sides of the salmon steaks with mixture. Barbeque on a well oiled grill over hot coals. Make a tent of foil or use barbeque cover and place over salmon. Barbeque 6 to 8 minutes per side depending on the thickness of your steaks. Baste frequently. Turn once, brushing with sauce. Steaks should flake easily when tested with a fork. Serves 4.