Place fillets or steaks in a saucepan, just cover with cold water, add salt, lemon juice, and cayenne, bring to a bubble, then turn down heat and simmer for 10-12 minutes. Remove fish, but retain the fish broth. Place fish in buttered baking dish. Stir together 1 cup fish broth and the cream. Melt 3 tablespoons of the butter and add minced onion, tarragon or marjoram. Cook just until onions are soft. Stir in flour and cook a minute or two. Then off hat, stir in 2 cups of the fish broth until smooth. Return to low heat, stirring until sauce begins to thicken. Spoon 2-3 tablespoons of the sauce into the beaten eggs, then stir the beaten eggs slowly into sauce. Add the cheese, stirring all the while and cook until uniform. Pour the sauce over the fish, dot with remaining butter, and bake in preheated oven at 190ºC or about 10-minutes to brown the sauce.