Peel cucumbers and cut them into thin slices. If they are very ripe, remove seeds. Mix with the salt, making sure that every slice is salted. Add more salt if needed. Let the slices stand for 30 minutes or, if you have time, for as long as 2 hours.
Meantime, peel the onion and cut into hair-thin slices. Place in a mixing bowl and add the sugar, paprika, vinegar an