We don't have a microwave. Is there an alternate solution to quick pickled onions? (Thanks!)
Yes -- you can bring the vinegar to a boil and pour it over the onion and beets. Let it cool and chill the mixture.
I was in the same pickle yesterday - I sauteed the onion in a little oil, then deglazed the pan with cider vinegar. Didn't have any beets so omitted them. Still good!