Take the herring fillets out of the package and let the oil drain off. In the meantime, cut the apple (without the skin), the onion and the pickles into very fine cubes and put everything in a bowl. Now cut the drained matjes fillet into very fine cubes and mix with the other ingredients.
Season to taste with lemon juice, pepper (possibly also a little salt) and dill and stir. If you like, you can also add some broth from the pickled cucumbers instead of the lemon juice. Let it steep in the refrigerator for at least 2 hours. Stir vigorously again before consumption.