Peel 1/3 of the lemon zest with the zest zipper. Season the fish with salt and pepper. Brush the piece of aluminum foil with oil, place the fish on it and sprinkle with the lemon peel, seal the aluminum foil tightly around the fish.
Cover the fish parcel in a saucepan with a little water and steam over low heat for about 5 minutes. Season the sauce with salt, pepper and sugar, remove the bay leaf.