Scrub and trim beets, leaving 1 inch of the stem and roots attached.

Using a mandoline or a sharp knife, slice vertically, root to tip, in ⅛-inch-thick slices. If your beets are large, you can cut them instead into batons about ¼ inch thick and 2½ inches long.

Divide the orange zest, garlic, fennel seeds, cumin seeds, and cinnamon stick evenly between the two jars. Fill the jars with the sliced beets, fennel, and onion.

Whisk the salt vigorously into the water until fully dissolved. Pour the brine over the beet mixture until completely submerged and brine comes up to the top of the jar. Because this is a relatively quick ferment, as long as your vegetables are submerged, you do not need to weigh them down. Reserve any leftover brine.

Place lids on the jars, but do not tighten. Alternatively, you can cover the jars with several layers of cheesecloth tied around the neck of the jar with twine.

Place the jars on a rimmed plate or ¼ sheet tray and leave out on your kitchen counter. Check the level of the brine after 24 hours and every day for about 5 days.

As the ferment starts to work, bubbles will rise up the walls and push some of the brine out of the jar. You can top up the jars with extra reserved brine (or make more) as necessary. Remember to keep the lids loose.

Taste the pickles as they sour and transfer it to the fridge to stop the fermentation process when you like the balance of salty, sweet, and sour flavors. Tighten the lids securely before storing in the fridge.

Cook’s note

If you prefer a pickle with a little sweetness, you can add 2–3 tablespoons of sugar or honey to each jar of beets before transferring them to the fridge. The fermentation process converts sugars into acids and carbon dioxide, but at cold refrigeration temperatures, this all but stops.