Wash the salmon and dab dry. Wash and chop the dill. Mix with mustard, freshly ground pepper and lemon juice. First season salmon with salt, then brush with the paste. Cover and chill for at least 30 minutes.
In the meantime, wash the potatoes and cook in boiling salted water for about 15 minutes. Then peel them and fry them all round in about 2 tablespoons of oil until golden brown shortly before serving. Peel cucumber thinly, wash and slice. Peel onions and cut into rings. Whip vinegar and 3 tablespoons of oil. Season with salt, pepper and sugar. Mix cucumber and onions with the marinade. Cut salmon into portions. Fry in the remaining hot oil while turning for about 5 minutes.
Whip vinegar and 3 tablespoons of oil. Season with salt, pepper and sugar. Mix cucumber and onions with the marinade. Cut salmon into portions. Fry in the remaining hot oil while turning for about 5 minutes. Serve salmon, potatoes and salad garnished with fresh dill and lemon