Thaw the salmon. Heat some butter in a saucepan and fry the onions until translucent. Add the cream and simmer on medium heat. Stir in some chopped chives and season the sauce with salt, pepper and lemon juice. If necessary, add a little sauce thickener to the sauce to get a creamier consistency.
In the meantime, dice the salmon or cut into fine strips. Cook the tortelloni according to the instructions on the packet and drain.
Put the salmon in the cream sauce and turn off the stove. Let the fish soak in the sauce for about 2 minutes, then pour the sauce over the tortelloni and enjoy.