This is a super simple method of cooking snapper but it requires a few days marination to make the lemon oil. Note that I am using a stovetop grill pan which has ridges to make nice grill marks. You could also do it on the barbecue.
Peel the lemon with a potato peeler, making sure you only get the peel and not the white pith. Pound the peel in a mortar and pestle with 2 tablespoons olive oil to release all the lemon oils, about 1 minute.
Scrape the contents of the mortar into a jar or plastic container and add remaining olive oil. Let marinate 4 days, then strain, discarding the peel.
Rub the snapper fillets with salt and pepper. Rub with lemon oil on both sides.
Heat up a ridge grill plate on the stove over high heat. Toss on the fish fillets and grill a few minutes each side to leave grill marks - do not overcook.
Transfer fish to warmed serving plates, drizzle with extra lemon oil and sprinkle with parsley. Done!