IF YOU WERE TO PLOT CONDIMENTS ON A FAMILY TREE, you’d find that these pickled red onions are the wild-child granddaughter of caramelized onion jam and the second cousin of the hot dog relish you find at the ball park. They are sophisticated, a little bit slippery, and equally at home draped across a hamburger or dolloped on a salad of baby arugula.
2 cups/480 ml apple cider vinegar
¾ cup/150 g granulated sugar
2 tablespoons pickling salt
3 pounds/1.4 kg red onions, trimmed and thinly sliced
2 teaspoons mustard seed
1 teaspoon celery seed
½ teaspoon red pepper flakes
Prepare a boiling water bath and 3 regular-mouth pint jars according to the process on page 10. Place the lids in a small saucepan, cover them with water, and simmer over very low heat.
Combine the vinegar, 1½ cups/360 ml water, sugar, and salt in a pot over high heat and bring the brine to a boil.
Add sliced onions to brine and stir to combine. Reduce heat to medium and simmer briefly to soften onions.
Meanwhile, combine the remaining spices in a small bowl and stir to blend. Add the spice blend to the sterilized jars, distributing evenly.
Using tongs, evenly divide the onions between the 3 jars. Pour hot brine into each jar, leaving ½ inch/12 mm headspace. Gently tap the jars on a towel-lined countertop to help loosen any bubbles before using a wooden chopstick to dislodge any remaining bubbles. Check the headspace again and add more brine if necessary.
Wipe the rims, apply the lids and rings, and process in a boiling water bath for 10 minutes (see page 11).
Let these pickles cure for at least 48 hours before eating.