Sift the flour, baking powder and a pinch of salt into a mixing bowl.
Mix the milk, kefir and eggs in another bowl, then add half of this mixture to the flour and combine. Gently fold in the rest with a flat wooden spoon.
Thinly slice the salmon and add to the batter together with the dill and oil. Rest for 15 minutes, if possible.
Meanwhile, make the horseradish sauce: mix the lemon zest with the kefir, lemon juice and horseradish. Set aside.
Oil a heavy-based saucepan, then heat. When piping hot, add dollops of the batter and let them spread out a bit. Cook for 2-3 minutes, then flip them over and cook for another minute or so until golden.
Transfer them to a plate, lined with kitchen paper towel.
Serve warm with the horseradish sauce.