Loosen the well drained sauerkraut, mix it with the chopped onions, pepper as well as the oil in a baking dish and let it soak for about 1 hour. Cut open the rye rolls and butter both sides (so that they do not become soggy).
Cover them with the sauerkraut mixture, on top of each a slice of salmon form. Decorate the rolls with a slice of boiled egg and caviar.