Pickled Red Onions

Author A Pleasant Little Kitchen | July 2, 2025

 

Author note: Don’t let the word “pickle” intimidate you. Pickled Red Onions is a simple, fast and versatile recipe. There is no “putting up” or “canning” in this recipe. It is a quick pickle that utilizes a mustardy brine to easily create pickled red onions in about 1 hour. Additional vegetables like cauliflower, carrots and garlic are a nice addition. Keep in mind that heartier veggies take longer to pickle.  

Ingredients

1 large red onion, halved and thinly sliced

1 tsp mustard seed

1 1/2 tsp kosher salt

1 tbsp sugar

Pinch of red pepper flakes

1/2 cup to 3/4 cup apple cider vinegar (depending on the size of the onion)

Instructions

Place the onion slices into a large, heat-proof bowl.

In a saucepan, add the mustard seed, salt, sugar, red pepper flakes and vinegar. Bring to a simmer and let cook until the salt and sugar are dissolved. Stir to combine.

Pour the brine over the red onions. Stir. Press down on the onions to submerge. Let cool for 30 to 45 minutes, stirring occasionally.  Place in an airtight container, store in the fridge and strain before serving.

Topics: A Pleasant Little Kitchen