Step 1

Place a steamer basket in a large saucepan, add 1 inch of water and bring to a boil. Put potatoes in the basket and steam until barely tender when pierced with a skewer, 15 to 20 minutes, depending on size. Slice each potato into 1/4-inch-thick slices (discard the ends). Sprinkle the potato slices with salt.

Step 2

Cut herring fillets into pieces small enough to fit on a potato slice. Place one piece of herring on each potato slice, dollop each with about 1/8 teaspoon sour cream and sprinkle with red onion. Garnish with dill and a grinding of pepper.