Simply slice the onion thin, add it to a mason jar, and pour the simmered vinegar mixture over the top. Seal and let them marinate in the brine. That's it!
Add all ingredients into a small saucepan, except for the onion. Bring it just to a simmer then remove from heat.
Slice your onion thin and add into a pint size mason jar. Carefully pour vinegar mixture over the onions.
Seal and allow onions to sit for about 45 minutes before use.
TIP - If your onions come a little too high compared to the liquid just flip your jar for half of the duration or push them down with a spoon periodically.
Notes
You can substitute the apple cider vinegar with distilled white vinegar.
Sub granulated sugar with either maple syrup, honey, raw, or cane sugar. You may need to play with the measurements if doing so.
These will keep well in the refrigerator with an air-tight lid for up to 2 weeks. These instructions are not for canning, just for refrigerator pickled onions.
Feel free to add garlic, peppercorns, or fresh herbs if desired.