This tangy and delightful condiment is a great addition to a salad, eggs, tacos, burgers, and more.
Combine apple cider vinegar, hot water, maple syrup, and sea salt in a medium bowl. Whisk together until maple syrup and salt are fully dissolved.
Place thinly sliced red onion and black peppercorns in a large wide mouth mason jar.
Pour vinegar mixture over the onions and black peppercorns.
Let jar cool for 30 minutes. Cover jar and place in refrigerator for at least 24 hours.
Enjoy! Pickled onions will last for a few weeks when stored in the refrigerator.