Thinly slice the zucchini into rounds (I use a mandolin to get a nice even slice).
Add the zucchini rounds to a half gallon jar or split between smaller jars. Add the red onion and garlic to the jar too.
Make the salt water brine by mixing ½ cup of warm water with the salt and stir until the salt has dissolved.
Add the remaining water to the salt water once the salt has dissolved. Add the turmeric and mix well.
Pour the brine into the jar with the zucchini. There should be enough to submerge the zucchini under the brine. If not, make more brine and add it to the jar.
Cover the jar loosely with a lid and store in a cool, dry place away from direct sunlight for 3-7 days.
Once the brine is cloudy, try a zucchini to see if it’s ready. It should be sour and smell like pickles. Store in the refrigerator for up to a month.