Cook the potatoes as jacket potatoes for about 20 minutes, leave to cool. Peel the onions and cut into rings. Wash dill, shake dry and chop. Mix the oil with lemon juice, salt and pepper.
Peel the potatoes and cut into slices with an egg cutter. Grease a large, flat baking dish. Layer in the potatoes, onions and the salmon cut into small pieces. Sprinkle with dill and pour the lemon-oil mixture over it.
Cook in the oven preheated to 200 degrees on the middle rack for about 20 minutes.