2 cups red onion, thinly sliced
1/2 medium chili pepper, thinly sliced (omit for a milder version)
2 tsp whole black peppercorns
1/2 cup apple cider vinegar (white wine vinegar or distilled white vinegar also work well)
1/2 cup water
2 Tbsp sugar
1/4 tsp sea salt
Thinly slice your red onions using a sharp knife or mandoline. Thinly slice the chili pepper, if using.
Pack the onion, chili pepper, and 2 tsp of black peppercorns into a wide-mouthed mason jar.
In a small saucepan, combine 1/2 cup apple cider vinegar, 1/2 cup water, 1/4 tsp sea salt, and 2 tablespoons of sugar. Heat the vinegar mixture over medium heat until the sugar has completely dissolved. Carefully pour the hot vinegar mixture over the onions.
Press the onions down so they are fully submerged. Set aside on the counter top to cool, uncovered, for 30-60 minutes.
Secure the lid on the mason jar and keep in the fridge.
Picture and recipe adapted from: https://www.heynutritionlady.com/spicy-pickled-onions/