Peel and slice the onions into thin rings as pictured, and pack them tightly into a sealable glass jar.
Next, put all the ingredients except the sliced onions in a small saucepan, and bring to a boil over medium-high heat. Turn the heat down and simmer the mixture for 2 minutes.
Pour the hot brine over the packed onions until completely submerged, leaving ¼- to ½-inch space at the top of the jar. Leave the jars of onions out on the counter with the lids off to completely cool.
Place the lid(s) tightly on the completely cooled jar of onions and place it in the refrigerator. The onions are ready to eat in 24 hours, but the longer they stay in the refrigerator, the more pickled they will be.
The pickled onions will keep for up to 6 weeks in the fridge.
Enjoy!
Recipe by Real Life Dinner at https://reallifedinner.com/pickled-onions/