Peel onion and cut into fine rings. Cut herring fillets diagonally into pieces. Wash the apple, rub dry, quarter, core and cut into slices. Drizzle apple slices with lemon juice.
Wash the cucumber, rub dry and cut into slices around the core with a peeler. Mix all ingredients. Season sour cream with salt, pepper and a few drops of lemon juice and fold in.
Wash the dill, dab dry and pluck flags, except some for garnishing, from the stalks and chop finely. Add dill to the salad and fold in carefully. Arrange salad and garnish with dill.
Sprinkle with coarse pepper.