Peel the potatoes, put them in a pan cover with cold water and salt.Boil for 12-15 minutes and drain. Let them cool slightly and cut into thin slices. Clean the onions, cut in slices and cut the tender, green part in diagonal pieces.
Preheat oven to 180 ° C. Put the fish fillets in the center of an oiled fireproof dish and place all around the potatoes, alternating with the onions and tomatoes. Add the bay leaves, thyme, salt and pepper, sprinkle with wine and 3 tablespoons olive oil, cover the pan with aluminum foil and put it in the oven for about 20 minutes.
Check if the potatoes are well softened, remove the foil and sprinkle with the remaining olive oil. Turn on the grill of your oven and out the pan back and leave for 5 more minutes, until the potatoes are golden brown. Serve the fillets directly from the pan.