- 4 cups 1/4-inch chunks watermelon rind
- 1 cup 1/4-inch chunks onion
- 1/4 cup salt
- 2 cups apple cider vinegar
- 1 cup white sugar
- 1 tablespoon finely chopped fresh ginger
- 1 clove garlic, finely chopped
- 3/4 teaspoon ground cinnamon
- 3/4 teaspoon dry mustard
- 1/2 teaspoon ground turmeric
- 1/4 teaspoon ground dried chipotle pepper
- 1/4 teaspoon ground cloves
- canning jars with lids and rings
- Stir watermelon rind, onion, and salt together in a large bowl; refrigerate until liquid has been released from the rind, about 24 hours.
- Combine vinegar, sugar, ginger, garlic, cinnamon, mustard, turmeric, chipotle pepper, and cloves in a large saucepan; bring to a boil. Decrease heat to low and simmer until sugar is dissolved, about 10 minutes. Add watermelon rind mixture and simmer for 30 minutes more.
- Sterilize the jars and lids in boiling water for at least 5 minutes. Pack piccalilli into hot, sterilized jars, filling to within 1/4 inch of the top. Run a knife or thin spatula around the insides of the jars after they have been filled to remove any air bubbles. Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids and screw on rings.
- Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars into the boiling water using a holder. Leave a 2-inch space between the jars. Pour in more boiling water if necessary to bring the water level to at least 1 inch above the tops of the jars. Bring the water to a rolling boil, cover the pot, and process for 15 minutes.
- Remove the jars from the stockpot and place onto a cloth-covered or wood surface, several inches apart, until cool. Once cool, press the top of each lid with a finger, ensuring that the seal is tight (lid does not move up or down at all). Store in a cool, dark area.