Condiments & Sauces

Fermented Red Onions

Fermented red onions are like happy little flavour bursts, enhancing just about anything they touch. As an added bonus they are perfect for a plant-based diet, which I’m not going to lie makes me pretty damn happy indeed! Plus as fermented food they are beneficial for our gut health. So that means they are both tasty AND healthy, which makes them a win-win situation. As if that wasn’t enough they are also super easy to make. Which by my calculations increases their rank to triple threat!

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As I transition (slowly) from a meat eater to a whole foods plant-based diet I am trying as much as possible to bring things from my old life into this new one. This isn’t a small life change, so anything that makes it easier is so welcome. My 5 step game plan is as follows…

  1. Transition from meat-eater to pescatarian.
  2. Transition from pescatarian to lactose-ovo vegetarian.
  3. Transition from lacto-ovo vegetarian to vegetarian.
  4. Transition from vegetarian to plant-based.
  5. Transition from pant based to whole food plant-based.

I really want this dietary change to stick and for me, that means taking it slow. If you were able to go from meat-eating to plant-based overnight then kudos to you! I just see myself falling off the wagon that way. So you do you and I will see how this 5 step plan I’ve concocted works out for me! But that’s enough about that, let’s take a look at these fermented red onions and the fermentation process that is going to take them from meh to amazing!


Here are some onions I grew last season. Unfortunately, I don’t have any left as I ate them all, but I am planning to grow a LOT more onions this upcoming season. I actually have to go start the seedlings tomorrow (yes in January). Why so early? Well, that’s due to the fact that I like to grow my onions from seed rather than from sets. Most people grow from sets as it shortens the growing time. But personally I don’t mind the extra time it takes and I can get a lot more types of onions for a lot cheaper using seeds.

What is lactic acid fermentation?

That’s a great question! So let’s take a moment to understand what is going on. Fermentation, in general, is a metabolic process that uses enzymes to create chemical changes. In our case, with lactic acid fermentation, we are relying on microorganisms to do all the heavy lifting for us. This process has been used by humans dating back to the Neolithic Age. The most well-known usage of fermentation is in the production of beer and wine. However, fermentation is also used to create such things as kimchi, kefir, sauerkraut, sriracha, and kosher pickles!

That’s all well and good but was IS lactic acid fermentation? The microorganisms (naturally occurring lactobacillus bacteria or LAB) that we are leveraging, like us, need to ‘eat’. As part of ‘eating’ (using sugars to produce cellular energy), they produce lactic acid, and it is this that makes the magic happen. This natural process only requires water and salt. You may be questioning that last statement seeing as I just said the process requires sugar, but then I listed water and salt! The sugars that are used are the ones naturally present in the onions.

The salt and water are just there to create a brine. This is important as the brine prevents the food from spoiling, but does not harm the lactobacillus bacteria. Most dangerous bacteria can not survive in salty environments, thus making salt a natural preservative! This is exactly what we leverage by creating a brine for our onions.

Now that we have all that out of the way, let’s look at making some of these delicious, fermented wee beasties. Oh, and they are probiotic too, which is good for our bellies (more specifically, our gut flora).

Fermented red onions

What you need

  • 500mL mason jars
  • Fermentation lids (I have ones like these, but these are good too)
  • Pickle Pebbles (these prevent any onions being exposed to air)
  • Sea salt or pink Himalayan salt
  • Water (many people suggest using distilled water to eliminate the possibility of any chemicals that could be lurking and damage our good bacteria)
  • Red onions
  • Mandolin or really good kitchen knife

So now we can get down to work. As I mentioned at the outset this isn’t hard to do. What IS hard is waiting for them to be ready! That said the sooner we begin, the sooner they will be ready to eat.

As with any canning or fermentation, you are going to want to start with a clean and sterile environment. So be sure to sterilize your mason jars and pickle pebbles before you start. I really love these ones by Masontops.

Pickle pebble

Sterilizing them is easy enough to do. Just grab yourself a large pot, fill it with water and set it to boil. Once it has reached a rolling boil, carefully lower your jars into the water (I suggest using canning tongs). Leave the jars in the boiling water for 10-15 minutes.

Sterilizing jars

While the water/jars are boiling, you are going to want to make up the brine so it has time to cool. In a small pot pour 1 cup of the distilled water and bring it to a boil.

Himalayan salt

Once it has boiled add in the salt and let it dissolve. I decided to use Himalayan salt because it’s pretty and more importantly it has loads of great trace elements in it. Once the salt has all dissolved you can add in the other cup of water to help cool it down a bit quicker. Don’t forget to take the mason jars and pebbles out of the water and set them aside on a clean towel to cool.

Red onions

Then you will need to go and grab yourself some red onions and your mandolin (or good quality knife). It’s time to get to work slicing yourself some onions. The thickness is up to you based on your mandolin or your knife skills.

I decided to slice mine pretty thin. As a side note, I make sure to save the onion ends and outer skins and put them in a freezer bag. I keep it in the freezer (along with other veggie scraps) and when it is full I make up some homemade vegetable stock (but more on that later).

Onion skins

If you don’t want to store the scraps in your freezer to make stock at a later date, why not compost them? If you already compost then well done my friend! If you don’t and would like to know how to get started you can check out this post about composting on my other blog ( yes I’m insane and have two blogs).

Fermented red onions

When your jars are cooled, your onions sliced and your tears wiped away it is time to fill the jars. Don’t pack them too full as we need to leave room for the pebbles, brine and headspace.

Fermentation weight

You are going to wait to leave about 3/4″ of space from the top of the brine to the edge of the jar. With the pebble place and packed down, you can carefully pour in the brine making sure to leave that headspace I mentioned.

Fermented red onions

Now you can add on the fermentation lid and you will want to step the jars in a cool, dark room for at least two weeks. You need to give them enough time to properly ferment. If you peek in on them during the first week you should see some bubbles. This is why its’ so important to use proper lids so that the gases can escape. After 2 weeks the fermentation should be well on its way.

The longer you leave them to more probiotics and tanginess you will end up with. That said there can always be too much of a good thing and I wouldn’t recommend going over 1 month. When they are to your liking you can remove the fermentation lid, screw on a regular mason jar lid. Personally, I really like these leakproof ones, I also use them when I take my lunch to work in mason jars. The cold of the refrigerator will stop the fermentation process.

Fermented Red Onions

Fermented red onions act like happy little flavour bursts, enhancing just about anything they touch. They are perfect for a plant based diet and as an added bonus they are probiotic.
Prep Time 30 mins
Cook Time 0 mins
Total Time 30 mins
Course Side Dish
Cuisine American
Servings 10
Calories 10 kcal


  • Mason jars
  • Fermenting lids
  • Canning tongs
  • Mandolin or good knife
  • Pickle pebbles


  • 2 Red onions
  • 1 Tbsp Sea salt or pink Himalayan salt
  • 2 Cups Water (Distilled is recommended)


  • Sterilize your mason jars and pickle pebbles in boiling water for 10-15 minutes. When done remove from the water and set aside on a clean towel to cool.
  • Thinly slice your red onions using a mandolin or good kitchen knife.
  • Boil 1 cup of water, remove from heat and dissolve the salt, then add in the second up of cold water.
  • Add the sliced onions to the cooled jar and cover with a pickle pebble.
  • Pour in the brine, leaving 1" of head space betweent the brine and top of the jar.
  • Screw on the fermenting lid and put the jar in cool dark place.
  • Leave for 2-3 weeks. The longer you leave them to tangier they will be.
  • Once they are to your liking, remove the airlock. Put on a mason jar lid and put them in the refrigerator. The cold will stop the fermentation process.
Keyword fermented, red onion

So there you have it, easy fermented red onions that taste great and are good for you! Want to grow your own onions? Check out my post on the 5 Things you need to know about growing onions.

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