Cook pasta al dente.
Dice the onion and fry until translucent. Add creme fraiche and cream, cook briefly and season with salt and pepper.
Half of smoked salmon cut into small pieces and add to the sauce. Heating, but not boil.
The other half of the smoked salmon cut into strips.
Puree the sauce with a hand blender, then heat briefly and mix well with the drained pasta. Lift underneath the strips of smoked salmon.