Defrost frozen salmon. Wash and clean the cucumber and peel it if necessary. Slice or cut the cucumber into thin slices. Wash the dill, shake dry and put some flags aside. Finely chop the remaining dill.
Stir sour cream, milk and 2-3 tbsp. lemon juice until smooth. Stir in dill. Season to taste with salt, pepper and sugar. Mix with cucumber and let everything simmer for about 20 minutes.
Wash the salmon, dab dry and cut into cubes. Season with salt, pepper and 1 tablespoon lemon juice. Heat oil in a coated pan. Fry the salmon for 2-3 minutes. Season cucumber salad again and arrange with the warm salmon cubes.
Garnish with remaining dill flags.