With Kingfish, Tuna etc the trick is not too overcook. Leave the skin on, generously salt and pepper , fry skin side down and cook until turns white almost to middle, flip and similar . If only just cooked to the centre or slightly raw, fish will be moist and tasty. Fry some onion beforehand and remove then throw them on top, drizzle olive oil and lemon juice to serve. Works well with pink salmon too.