Arrange the fillets in a greased oven dish, sprinkle them with salt, pepper and a little lemon juice. Mash or grind the dried tomatoes with olive oil, mustard, walnuts and onions in a food processor, adding a little water to make a smooth, thick paste.
Brush the fish fillets on all sides with it. Sprinkle each fillet with breadcrumbs and parmesan cheese on top and put it to bake for 15-20 minutes in a highly heated oven.
Serve the oven baked fish fillets with lemon slices.