Pickled red onions take minutes to throw together and add a briny-sweet-spicy crunch that kicks up the flavor and texture in all kinds of dishes, like tacos, salads, wraps, and more.
On a cutting board, trim off both ends of the onion and discard the outer skin. Cut in half from top to bottom. Lay both halves flat side down and then slice very thinly vertically (from top to bottom). (Alternatively, you can use a mandolin to slice the onions.)
Pack the onions down into a 16-ounce jar.
In a small pot, add the water, both vinegars, sugar, salt, and (optional) red pepper flakes. Bring to a boil and then remove from the heat.
Pour this brining mixture over the onions, screw on the lid, and place in the refrigerator for at least 2 hours. These taste best if eaten within about 3 days, but can remain in the fridge for 2-3 weeks.
Notes
Pickled red onions taste best if eaten within about 3 days, but can remain in the fridge for 2-3 weeks.