Bring the vinegar, wine, sherry, sugar and spices to the boil. Add onion rings and simmer for 5 minutes over low heat. Let cool down. Pat dry herring fillets and place in a container. Pour the cooled marinade over it. The matjes must be covered. Close the jar and let it steep in the refrigerator for two, or better three, days.
It goes well with boiled or jacket potatoes
If the whole is used as a side dish, cut the fish into 2-3 cm thick pieces before serving