Halve the white and light green part of the leek, wash thoroughly under running water (including the inside of the leaves) and cut into strips about 1 cm wide.
Peel the potatoes, cut them into cubes and put them in a saucepan with the leek, pour in the stock and the wine and cook until very soft, this takes a good 30 minutes.
Puree everything in the blender or with the hand blender. Stir the créme fraiche into the vegetable puree, bring to the boil briefly and season with salt and white pepper and a touch of grated nutmeg.
Finally add the salmon and tomato cubes, heat them up briefly (do not let them boil anymore) and sprinkle the soup with chopped dill. Serve well hot.