Cut fish into cubes, put in a cool place.
Peel onions and garlic, chop finely and sauté in oil.
Wash zucchini, cut away stem ends and cut in half lengthwise.
Hollow out the halves, cut the flesh into cubes and steam in butter for 5 minutes until soft, let cool.
Mix eggs with breadcrumbs, add to zucchini. Fold in fish cubes. Season everything with nutmeg, pepper, salt, thyme and finely chopped parsley.
Cut the tomatoes, put them in boiling water for a short time, remove the skin and cut them into cubes.
Preheat oven to 200 °C.
Blanch zucchini halves in salted water for 3 minutes, fill with fish mixture.
Place in a well greased ovenproof dish. Spread the diced tomatoes and vegetables evenly inside and season with salt and pepper.
Bake on the middle shelf for about 20 to 25 minutes.