Peel the onions and do not dice too small. Put the sugar in a heavy-bottomed saucepan, let it melt over medium heat without stirring. When the sugar begins to turn a light brown color, add the onion cubes and let them take on some color, stirring constantly.
Then pour apple cider vinegar and water on it, add salt, pepper, clove and bay leaf and let everything simmer slowly for about 1 hour.
The onion relish is ready as soon as the liquid has almost completely boiled away.