Peel and thinly slice onions. I use a food processor. Sprinkle sumac over the onions and stir to coat.
Firmly pack the onion mixture into 2 quart sized mason jars and leave an inch of head space.
Mix together a 3.6% brine by adding 2 tbsp unrefined sea salt into 1 quart of non-chlorinated, filtered water. Stir to dissolve.
Pour brine solution over onions. Press onions down so they are under the liquid. At this point you can cover with a cabbage or grape leaf and weigh down with a sterilized rock or fermenting weight. Keep the 1 inch head space. I am using a homemade airlock system, but it’s not necessary. You can just cap them with a canning lid.
Set out of the way on the counter and cover with a cloth to block out light. Leave on counter for 3-7 days before transferring to refrigerator. Watch for signs of fermenting after a couple days. You should see small bubbles trapped on sides. After 3-4 days, smell to see if has the sour fermented smell. Use a clean fork to test a piece. If not to your taste leave out a few days longer. Will keep 6 months in fridge.
Note:Ferments happen slower in cooler weather. Also, if you choose to use a starter, such as whey, only use 1 tbsp of salt in your brine and leave on the counter only 2 days as the starter greatly speeds up the fermenting process.
Lacto-Fermented Sumac Onions
I first tasted sumac onions at my first visit to a Persian restaurant. Right away, I was hooked and was putting these sour marinated onions on everything, with extra sumac shaken on. Love that stuff! Since then, I have been wanting to create a fermented version for extra nutrients. Serve with just about any Middle Eastern dish!