Sterilize your jar: I do this by placing my jar in a clean sink and pouring boiling water over it. Alternatively, fill the sink with boiling water and submerge the jar.

Remove the jar to a clean area on your counter and allow it to cool before using it.

Peel and slice your onions.

Prep the brine: I haven't included amounts in this recipe, because I like to do it by weight! I recommend making the brine with 3% salt by weight if you ARE using whey, or 5% salt by weight if you are NOT using whey.

To mix your brine, weigh about 2 cups of water, in grams. Calculate your salt: amount of water (in g) x .03 (or .05) = grams of salt. Add your calculated weight of salt to your water, and mix to dissolve salt.

Add your sliced onions to your prepared jar.

Add a generous pinch of sugar and whey, if using.

Pour brine over onions. Make sure the brine fully covers the onions, to avoid mold. Fermentation weights can help ensure that the onions stay submerged!

Cover your jar. If you use the regular lid, make sure to remove it once a day while the jar is on the counter, to release any built up gas from fermentation.

Leave the jar on the counter at room temp to ferment. Fermentation time varies by room temperature, but will likely take about 4-7 days. Begin tasting after four days, if you are seeing some signs of fermentation, like bubbles appearing in the jar.

When fermentation is complete, remove weights, tightly cap jar and move to the fridge.