In a small saucepan mix apple cider vinegar, water, salt and sweetener to taste. Turn on the heat and cook over medium heat until the liquid comes to a boil.
Slice the onions into half moons quite thinly. Put them in a glass jar. Pour the hot vinegar mixture over the onions, if necessary gently push them down to fully submerge. Screw on the lid and leave to marinate at room temperature for at least 30 minutes. Once completely cold, serve them according to your preferences.
You can enrich the flavor of the onions by adding different types of spices such as bay leaf, juniper, cinnamon, chilli pepper, garlic, etc.
Note from the author of this recipe
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Notes
The nutritional values are generated automatically for indicative purposes only and are therefore not completely accurate.