Crab cakes, pit beef … and onion pickles? The Baltimore staple you may not know.

I had made a grave error. “Do you have memories of eating pickled onions?” I asked in a post on the Facebook group “Baltimore Past & Present Photos.” I had shared a photo of a jar of whole sour onions I had purchased at Baltimore’s oldest Italian deli. I was quickly — and repeatedly — corrected by members of the more than 89,000-person-strong Facebook group: In Charm City, they’re called onion pickles, not pickled onions.