Wash the cucumber, grate dry and cut into fine slices. Season with salt and let it stand for 5 minutes. In the meantime peel onion and cut into fine rings. Wash dill, shake dry and pluck flags from the stems.
Chop the dill finely. Season vinegar with sugar and pepper. Fold in 1 tablespoon of oil and add dill. Drain cucumber water and mix with the vinaigrette. Heat 2 tablespoons of oil in a frying pan and fry the fish fingers for 5-8 minutes.
Take out and drain on kitchen paper. Cut the hot dog buns open lengthwise. Cover the bottom half with cucumber salad, 2 fish fingers and 1 tablespoon tartar sauce. Place the upper half on top.