Place quartered and sliced red onion into a quart mason jar or other container (glass preferred).
Whisk together the water, vinegar, sugar, salt, and pepper in a small saucepan over medium-high heat. Bring to a boil.
Pour hot liquid over onions in jar until liquid reaches just below the top of the jar. Discard any leftover liquid if there is any. Cool onions slightly, then cover and refrigerate overnight.
SNAPPY TIPS: You don't really need to measure the onions. Just peel, quarter, and thinly slice your onions and fill a quart mason jar to the top without over stuffing them in. I suggest making the recipe as is to begin with then experiment with your favorite vinegars and/or spices the next time. Make sure the water and sugar liquid is hot when you pour over the onions. Keep the onions stored in the fridge.
SNAPPY SUBSTITUTIONS: Instead of white vinegar you can experiment with your favorite vinegars. You can also experiment with your favorite spices.
Keywords: how to make pickled onions, summer pickled vegetables