Wash the potatoes and cook in boiling water for 15-20 minutes. Rinse in cold water, peel and leave to rest for a while. Meanwhile peel onions and garlic, dice finely. Wash thyme, shake dry, chop.
Cut the dried tomatoes into fine strips. Wash the fish fillets and dab them dry. Sprinkle with lemon juice and olive oil and salt. Cut potatoes into slices and place them on a tray or in a large dish.
Season with salt and pepper. Spread the fillets on top. Sprinkle with other prepared ingredients. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes.