Wash the potatoes, cover and cook in water for about 20 minutes. Meanwhile wash lemon and cut into slices. Wash trout and pat dry. Rub inside and outside with the juice of 2 lemon wedges and salt.
Spread the remaining lemon wedges into the trout, except for a few for garnishing. Rinse and peel the potatoes.
Place the trout and potatoes on an oiled baking tray. Season potatoes with salt. Spread butter in pieces on the potatoes and trouts. Bake in a preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see
manufacturer) bake for about 30 minutes.
For the salad peel the cucumber and slice it. Clean, wash and cut the salad into strips. Mix sour cream, milk, mustard, vinegar and oil. Season with salt, pepper and sugar. Mix with salad and cucumber.
Wash the dill, shake dry and pluck off the tips.
Arrange trout and potatoes. Garnish with lemon wedges and dill. Serve with cucumber salad.