There a few Latin American chicken places around Baltimore and DC that serve a chicken sammie that has what looks to be pickled red onions on top.
I have tried to make my own, assuming you boil water with vinegar and sugar and then steep the onions in it for a while.
It never comes even close to tasting as good as the palces I visit. Not only do they not taste as good, I also never get the soft texture and brillant red color these places do.
Any tips? Maybe a basic ratio rule?