Think pickled red onions but with a Mediterranean twist! These balsamic vinegar pickled onions are going to become your new favorite things to add to Mediterranean salads, sandwiches, and grilled summer vegetables.
Balsamic vinegar is naturally sweeter than red wine vinegar or white vinegar, which makes it the perfect choice for pickled onions. While its dark color may scare some people off, the onions look bright pink once they are out of the brine.
This recipe combines the flavors of a classic balsamic vinegar dressing with the pungent taste of red onions. If you like it, make sure to also give these red wine vinegar pickled onions and these pickled yellow onions with dill and mustard seeds a try.
What is quick pickling?
Unlike fermentation, quick pickling uses vinegar and sugar to pickled onions and other vegetables (such as these pickled carrots or this pickled cauliflower). In this case, the sliced onions are soaked in a sweetened vinegar and water mixture and stored in the refrigerator for up to 2 weeks – hence why they are sometimes called refrigerator pickles.
Key ingredients and substitutions
- Red onions: they are my go-to onion variety as they pair really well with balsamic vinegar and Mediterranean recipes.
- Balsamic vinegar: I like to use high-quality balsamic vinegar, preferably made with minimal ingredients and without flavorings. You can substitute it with apple cider vinegar, which has a similar amount of sweetness, or check out this red wine vinegar pickled onions recipe.
- Sugar: balances out the tartness of the vinegar.
- Salt: increases the preservation time of the pickled onions.
- Spices: add a ton of flavor. To keep it simple, simply add black peppercorns and oregano or Italian herbs. You can also add fennel seeds for an anise flavor, and red pepper flakes for some heat.
- Fresh herbs: I LOVE adding fresh herbs to my pickled onions. Fresh thyme or rosemary would pair really well with the other flavors of this recipe.
- Prepare the brine in the microwave to save time. Make sure the brine is hot and the salt and sugar have dissolved.
- Use 16-ounces (500 ml) Weck or Mason jars. They have the perfect size to fit 2 medium-sized red onions or 3-4 small ones.
- This recipe gets even better over time, so don't feel rushed to eat them all right away.
Step-by-step instructions (with pictures)
STEP 1: Prepare the balsamic vinegar brine. Add the water, vinegar, salt, and sugar to a small saucepan. Simmer until salt and sugar have completely dissolved.
STEP 2: Slice onions very thinly with a sharp knife of a mandoline.
STEP 3: Add the onion slices to a clean glass jar. My go-to is this 16-ounce (500 ml) Weck jar.
STEP 4: Pour the warm vinegar mixture on top. Make sure the onions are completely covered and leave about ½ inch (1 cm) room at the top.
STEP 5: Add in the dry spices. Give everything a good stir. Wipe off the rim of the jar and close it with a lid.
STEP 6: Let it cool on the counter until it reaches room temperature. Then, place it in the refrigerator for at least 20 minutes or preferably overnight.
How to serve balsamic vinegar pickled onions
- As a salad topping: they would go really well with this Mediterranean tomato and cucumber salad.
- On a sandwich: think about a generously filled grilled vegetable sandwich.
- In a wrap: check out this vegan pesto wrap.
- On a pizza: this lemony white sauce pizza with spinach could really benefit from pickled red onions.
Frequently asked questions
You can keep the pickled onions in the refrigerator for 2 weeks. Make sure the onions are completely submerged in vinegar brine the entire time.
If the onions look or feel slimy, it's preferable to throw them out. If some pieces were not submerged in pickling liquid, they may have gone bad as well.
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Balsamic Vinegar Pickled Onions
- 16-ounces Weck jars 500 ml
- 2 medium red onions
For the vinegar brine
- ⅔ cup (160 ml) balsamic vinegar
- ⅔ cup (160 ml) water
- 1 tablespoon sugar
- ½ teaspoon salt
Herbs and spices
- 1 teaspoon dried oregano
- ¼ teaspoon black peppercorns
- ¼ teaspoon fennel seeds optional
- ¼ teaspoon red pepper flakes optional
- 1 sprig fresh oregano optional
- Add the balsamic vinegar, water, salt, and sugar to a small saucepan. Heat over medium heat until the salt and sugar have completely dissolved.
- Slice the red onion very thinly with a sharp knife or a mandoline.
- Add the sliced onions, dried oregano, black peppercorns, fennel seeds, red pepper flakes, and fresh oregano (if using) to a clean glass jar. Pour the warm vinegar brine on top and close the jar with a lid. Let it come to room temperature.
- Place in the refrigerator overnight or at least 20 minutes before serving.
- You can store these pickled onions in the refrigerator in an airtight container for 14 days.
- Use on salads, such as this Mediterranean tomato cucumber salad, sandwiches, and wraps.
- Always make sure the onions are completely covered in vinegar brine. Onion pieces that were not submerged in vinegar are prone to bacterial growth.
- If they feel slimy or if some onions were not covered with pickling liquid, it's best to throw them out.
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