These are one of the easiest vegetables to ferment.
Great on burgers, salads, or just as a side dish.
wide mouth glass quart jar
2-3 onions, white, yellow, or red
a scant TBSP of kosher or 1/2 TBSP sea salt (must NOT contain iodine)
enough filtered or spring water to fill a quart jar full of onions
optional: peppercorns, herbs, spices
Peel the onions, save the peels.
Slice one “cap slice” from the top of the onion so you will have a solid dome. Slice it so you can later wedge it just under the shoulders of the top of the jar. This will be used to keep your food under the brine.
After getting your “cap slice”, slice the remaining onions, thick or thin, it’s up to you. Are you going to put them on a salad or a burger? Slice them how you’d think you’ll use them. If you slice them bigger, you can always cut smaller after fermentation.
Add a cup of water to the quart jar, add your salt and shake to dissolve.
Pack the jar with your onion slices, adding herbs and seasoning along the way. You can add the peels if you like. I would add them at either the top or bottom. You won’t want to eat them, but they do contain a lot of flavor, and with red onions, they will add extra color…and that’s a good thing! Pickled red onions are a beautiful color, and will be a great visual accent to your meals.
Add more water to nearly fill the jar.
Here is the important part: you want your food to be completely submerged under the brine. If you were able to cut the “cap slice”, wedge it under the shoulders of the jar, and then add enough water so that it is completely submerged with brine.
Set the jar on a plate, or a plastic container that will catch any drips.
Cover the jar with a piece of cloth. A clean washcloth is great, a dishtowel, anything that will breathe and keep out any insects, like perhaps a stray fruit fly.
Let your jar of onions sit out at room temperature for 3-10 days. Onions seem to ferment pretty quickly. And the timing will affect the “pucker strength”. Shorter times will be milder, longer times will be stronger. You can always do a taste test along the way. Once you are happy with the flavor of the onions, add a lid and move them to the fridge. This will stop the fermentation and they should then keep for a VERY long time. Fermented foods rarely spoil, as the process is natural way of preserving foods. Things like fermented cabbage were taken on long sailing trips to feed the crew with no refrigeration necessary.
You will find that fermenting onions tempers some of the harshness of the onion, and adds a zing to them that is pretty irresistible. Fermented onions are one of my most favorite fermented foods.
As far as seasoning, it is up to you. I have fresh herbs in my garden. I love rosemary and sage with onion, either together or separate. Think of classic dishes you love and use combinations that match those, like Italian, or Greek, German, etc.
Enjoy using your fermented onions! Use the brine when you are done. You can do brine shots, or use the brine in salad dressings, marinades, etc. And remember that while you may certainly cook with fermented onions, any heat beyond a gentle warm (~105 degrees) will kill the wonderful probiotics you worked hard to create. Keep adding fermented foods to your diet and you will have a strong immune system!