Peel the red onion and slice it thinly. You can use a knife or a mandoline slicer for even, thin slices.
In a small saucepan, combine the white vinegar, water, sugar and salt. Bring the mixture to a simmer over medium heat, stirring until the sugar and salt have dissolved. Remove the pan from heat and let the mixture cool for a few minutes.
Place the sliced red onion in a clean jar or airtight container.
Pour the warm pickling liquid over the sliced onions, making sure they are fully submerged. If needed, use a spoon to press the onions down. The pickling liquid should cover the onions completely.
Let the pickled onions cool at room temperature for about 15-30 minutes. Then, cover the jar or container and place it in the refrigerator.
Allow the pickled onions to marinate in the refrigerator for at least 1 hour, but preferably overnight. The longer they sit, the more the flavors will develop.
Video
Notes
The pickled onions can be stored in the refrigerator for up to two weeks.Pickled onions are a versatile condiment that can add a tangy and flavorful punch to various dishes, such as sandwiches, salads, tacos, burgers, and more. Enjoy!