Salt and pepper the fillets with black pepper and a very light pinch of cayenne pepper. Place them in a heat-proof dish with a cover. Mix 3 tablespoons of butter, the shallots, tomato sauce, 1 cup of the cream, the lemon juice and white wine. Pour this mixture over the fish, cover, and let it simmer slowly for about 20 minutes, or until the fillets flake easily. Lift the fish onto a warm platter. Add the other cup of cream and the parsley to the sauce, and bring to a boil. Let it cool until the sauce thickens; then pour over the fish.