Slice (or dice, whatever you want) the red onion
Stuff the red onion into a jar (I used multiple 8oz jars)
Add in salt and garlic (and optional ingredients if using)
Pour in raw red wine vinegar until jars are full (you might use a little more or less than a cup). If you want a less potent pickled onion, you may dilute with distilled water (it must be distilled water though to promote probiotic activity)
Let the mixture sit for AT LEAST 2 hours (even better if you can wait 24 hours) before enjoying!
Good in the fridge for AT LEAST a week but perhaps longer (use your best judgement).