Drizzle the fish with lemon juice. Heat 1/2 tablespoon butter. Quarter the tomatoes and fry them in the fat. Place in a baking dish. Peel and dice the celery. Also fry in butter. Dice the fish and layer alternately with tomatoes and celery in the dish and season with salt.
Heat the remaining fat and sweat the flour in it. Add the cream and stir. Heat, season to taste and pour over the fish and vegetables. Cover with cheese and breadcrumbs and bake at 200 ° C for 45 minutes.