1. Preheat oven to 425 degrees Fahrenheit.
2. Chop the onion.
3. Into a soaked RomertopF, line bottom with a layer of fish and then add a layer of sliced bacon, sliced mushroom and finally sliced tomatoes.
4. Sprinkle chopped onion on top.
5. Cover the top with another layer of fish.
6. In a bowl, mix lemon juice with wine, tomato puree, salt and pepper; pour all over the fish.
7. Cover and cook for about 40 minutes.
8. Serve toasts alongside Fish Fillets with Mushrooms.