The vegetable onions are cut into approx. 0.5 cm thick slices or rings, depending on the desired size. Put the onions in a bowl.
Sugar and vinegar are mixed together and poured over the onions. Cover the whole thing and let it steep in the refrigerator overnight for at least 12 hours. The next day, pour off the liquid and stir in the mayo and season with salt and pepper.
The quantities given can be varied. The only important thing is the 1 to 1 ratio of sugar and vinegar. All of the onions should be covered with the liquid. Stir in the mayo depending on the desired creaminess.