Salted herring and onion salad

2 medium herrings,
3 big onions,
4 oz/100 g olives,
2-3 tablespoons oil,
2-3 tablespoons vinegar

Split the herrings lengthwise on their belly, remove roe and keep in tepid water for 5-6 hours. Then wash in cold water, skin them starting from the head to the tail, remove the backbone with all big bones, cut in pieces about two fingers thick and then arrange them side by side on a long platter, so that to resemble the whole fish. Peel the onions, keep them in cold water and then slice very thinly. Arrange the onion slices around the fish and on top of them the pitted olives. Pour the oil and vinegar dressing. Serve with potatoes or rye bread.