Wash the fish fillets and rub with salt and pepper.

Place on a platter, pour over the lemon juice and leave to marinate for about one hour. Drain.

Brush a medium sized baking dish with a little of the olive oil.

Line the baking dish with a layer of onion slices and sprinkle with the chopped parsley and the garlic.

Arrange the fish fillets on top of the onions and top with the tomato slices.

Pour in the remaining olive oil and the wine.

Sprinkle with salt and pepper to taste and bake in a moderate oven for about 30-40 minutes.

Serve either warm or cold.