Cut the red onion into half rings, squeeze out the garlic with a press and mix everything.
For the marinade, take a glass of hot (but not boiling, otherwise the onion will cook) water, add salt, sugar and vinegar. I used wine, but given the ratio of volumes of water and vinegar, I assume that the table can be taken in the same volume.
Mix thoroughly and pour into a mold with onion and garlic, the water should cover them completely, if not enough – just add more hot water.
Close the lid and leave to marinate for an hour.