Prep the Zucchini Mixture

1. Combine shredded zucchini and chopped onion in a large bowl. Sprinkle with canning salt and mix thoroughly.
2. Cover the bowl and refrigerate overnight to release excess moisture.

2. Rinse and Drain

1. Drain the zucchini mixture in a colander and rinse under cool water to remove excess salt.
2. Squeeze out as much liquid as possible and set aside.

3. Make the Relish Base

1. In a large pot, combine sugar, vinegar, red and green bell peppers, cornstarch, celery seed, nutmeg, turmeric, and black pepper. Stir well.
2. Add the drained zucchini and onion mixture to the pot.

4. Cook the Relish

1. Bring the mixture to a boil over medium-high heat, stirring occasionally.
2. Reduce the heat to medium-low and simmer for 30 minutes, stirring occasionally to prevent sticking.

5. Sterilize the Jars

1. While the relish simmers, sterilize the jars and lids using a boiling water bath or dishwasher sterilization setting.
2. Keep the jars warm until ready to use.

6. Pack the Jars

1. Ladle the hot relish into the sterilized jars, leaving ½ inch of headspace.
2. Remove any air bubbles by running a knife along the inside of each jar. Wipe the rims clean and screw on the lids.

7. Process in a Water Bath

1. Place a rack in the bottom of a large stockpot and fill it halfway with boiling water.
2. Lower the jars into the pot, ensuring they’re covered by at least 2 inches of water.
3. Bring the water to a full boil, cover, and process for 30 minutes.

8. Cool and Store

1. Carefully remove the jars and place them on a towel-lined surface to cool.
2. Check the seals once cooled—press the center of each lid; it should not move. Store sealed jars in a cool, dark place for up to one year.