1 medium red onion, thinly sliced

¾ cup water

⅔ cup apple cider vinegar

3 tablespoons granulated sugar

1 ½ teaspoons kosher salt

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Slice the Onion: Thinly slice the red onion. Use a mandolin for uniform slices if you have one.
Optional Rinse: If your onion is very strong, rinse the slices under hot water for 1 minute to reduce the sharpness.
Boil the Pickling Liquid: In a saucepan, combine water, apple cider vinegar, sugar, and kosher salt. Bring to a boil, stirring until the sugar and salt dissolve.
Add the Onion: Add the sliced onions to the boiling liquid and cook for 1 minute. Remove from heat, cover, and let it sit for about 20 minutes.
Refrigerate: Transfer the onions and pickling liquid to jars or containers. Let them cool to room temperature before refrigerating. Allow them to chill for at least 24 hours before serving.

For a different flavor, try substituting apple cider vinegar with white wine vinegar, rice vinegar, or balsamic vinegar.

Spice things up by adding peppercorns, garlic cloves, or cinnamon sticks to the pickling liquid.

Once the pickled onions are gone, use the leftover liquid as a base for a zesty salad dressing.