Combine the vinegar and barbecue rub in a bowl.
Place the onions in a freezer bag and pour the seasoned vinegar over them.
Seal the bag, removing as much air as possible. Shake the bag a little bit to make sure the onions are covered in vinegar.
Freeze for at least 12 hours, thaw in the refrigerator, then pile them high on a burger. Once thawed, the onions will keep for about 3 days.
1/3 cup vinegar
2 tsp. barbecue rub (such as Vernons BBQ rib or beef rub)
½ medium-size yellow onion, thinly sliced
2 tsp. barbecue rub (such as Vernons BBQ rib or beef rub)
½ medium-size yellow onion, thinly sliced
This article appears in May 2013.