2Cover potatoes with water in a medium saucepan and season well with salt. Simmer, uncovered, until just tender, 12 to 15 minutes.
3While potatoes cook, pat salmon dry and season with a rounded 1/2 teaspoon salt (total). Put salmon in a lightly oiled 4-sided sheet pan and press pepper on top. Bake until just cooked through, 8 to 10 minutes.
4Drain potatoes, then transfer to a bowl and very coarsely mash. Stir in oil and dill and season with salt.