Ingredients
Scale
- 1 medium red onion, thinly sliced
- Sea salt or kosher salt, by weight (use 2% salt-to-onion weight; about 3 g for a 150 g onion)
- 2 cups filtered water, at room temperature
- 1 Tbsp whey (optional, for faster fermentation)
- Pinch of sugar, to help start fermentation
Instructions
- Weigh the sliced onion to know the salt amount. Multiply the onion weight by 0.02 to get salt grams.
- Dissolve the measured salt and pinch of sugar in the 2 cups of filtered water to make a brine.
- Pack the sliced onion tightly into a clean jar, leaving about 1 inch of headspace at the top.
- Pour the brine over the onions until fully covered. Press the onions down so they stay below the brine.
- Add 1 Tbsp whey if using; it helps speed up fermentation but is optional.
- Cover the jar with a loose lid, fermentation airlock, or a cloth secured with a rubber band.
- Place the jar on the counter away from direct heat. Ferment at room temperature for 3–7 days, checking daily.
- Taste after day 3. When the flavor is pleasantly tangy, seal the jar with a tight lid and move it to the refrigerator.
Notes
Keep onions fully submerged in brine to prevent mold. If a white film forms, skim it off; it’s harmless but can affect taste.
- Prep Time: 10 minutes
- Cook Time: 4320 minutes
- Category: Condiment
- Method: Fermenting
- Cuisine: American
- Diet: Vegan, Gluten-Free