Combine butter, oil, lemon juice, tarragon, lemon peel and pepper flakes to make a marinade. Place fish steaks on broiler and brush with half the marinade. Broil under pre-heated broiler, 2 inches from heat, for 4 minutes. Turn the steaks, brush with remaining marinade, and broil until fish flakes to fork (about 4 more minutes). Salt and pepper to taste and serve immediately with lemon wedges. Also for: Use cobia, king mackerel, grouper or other large fish steaks