Chop the onion finely and fry in the butter until golden. Repaid with vermouth, make the cream and add the crème fraîche. Put salt, pepper, sugar, lemon juice and finely chopped dill. Allow to boil quietly a few minutes until it begins to thicken. Insert spinach, seasoned with nutmeg. Allow to boil for about 10 minutes, until spinach is tender and settles. Salmon cut into chunks, added with shrimp in the sauce and boil for another 5 minutes, without stirring much to not disintegrate fish. Boil the pasta al dente, drain and mix in the sauce. Serve with a dry white wine.