Wash and clean the cucumber and cut or slice it thinly. Radishes clean, wash and cut into thin slices. Wash dill, pluck flags from the stalks and chop finely, except for something to garnish.
Lightly roast sunflower seeds in a pan without fat, remove. Mix yoghurt and lemon juice, season to taste with salt, pepper and sugar, stir in chopped dill. Mix cucumbers and radishes, arrange in small bowls.
Spread yoghurt on top, sprinkle with sunflower seeds and sprinkle with dill flags and lemon zests.