Cut the washed, peeled cucumber into 1 cm thick slices, layer with the salt in a bowl overnight and cover with a cloth. The next day, pour the cucumbers onto a sieve to drain and dry with a cloth.
Layer the cucumbers and onions alternately with the remaining spices in a stone pot or in glasses. Bring the wine vinegar to the boil with water and sugar and pour it over the cucumbers while hot. After 8 days, pour off the vinegar, bring to the boil, stir in the preserving aid and pour it hot over the cucumbers again.
After cooling, tie the pot with parchment paper or preserving skin and store in a cold and dark place.