Start 2 or 3 cups of water on to boil.
Peel and thinly slice the onion into approximately 1⁄4-inch moons.
In the container you will be using to store the onions, add the sugar, salt, vinegar, and any flavorings. Stir to dissolve.
Place the onions in the sieve and place the sieve in the sink. Slowly pour the boiling water over the onions and let them drain. (This is a shortcut version of “blanching” the onions.)
Add the onions to the jar and stir gently to evenly distribute the flavorings.
Your quick pickled onions will be ready in about 30 minutes, but are better after a few hours.
Store in the refrigerator. They will keep for several weeks, but are best in the first week.
Adapted from thekitchn.com