Wash and clean the cucumber, cut in half lengthwise and scrape out the seeds. Cut the cucumber into slices. Peel and halve the onion and cut into thin slices. Wash salmon and dab dry. Season with salt and pepper.
Heat the oil in a coated pan and fry the salmon for 3-4 minutes on each side. Take out and keep warm. Sauté onion and cucumber in the frying fat. Season with salt and pepper, cover and stew for about 5 minutes over a mild heat.
Bring 150 ml of water to the boil, stir in broth. Stir flour and sour cream until smooth. Stir the mixture into the boiling broth and let it simmer for about 5 minutes. Wash the dill, dab dry, put something aside for garnishing.
Finely chop the rest. Stir the dill into the sauce, season with salt and pepper. Arrange everything together and garnish with dill.