The tomatoes are parboiled with boiling water, peel them and cut them into cubes.
Occasionally stir, to prevent burning. Chop the olives, celery and capers and add them to the tomatoes. Sprinkle with parsley and season with black pepper and salt, if necessary.
Arrange the fillets in a greased baking dish and pour on the mixture from the pan. Cover with foil and bake for about 20 minutes in a 428°F (220 °C) oven.