Onions peel, finely dice. Heat the fat in a pot, add the onions and sauté. Sweat flour in it. Add cream and stock while stirring constantly, bring to the boil. Wash and chop dill and thyme.
Cut salmon into strips. Stir the herbs and salmon into the sauce. Season to taste with salt, pepper and lemon juice. Heat ravioli in boiling salted water for 1 minute, drain. Serve with the sauce on plates.
Serve garnished with lemon.