Wash your mason jars and lids in hot soapy water, rinse, and let air dry.
In a saucepan combine 1 cup of apple cider vinegar and 1 cup of water and cook over high heat. Once brought to a boil, stir in 1 tablespoon of kosher salt and 2 tablespoons of cane sugar till dissolved. Set the brine aside to cool slightly.
Thinly slice 1 pound of red onions and pack into jars, making sure there is a ½-inch of space from the rim of the jar to the tops of the vegetables.
Pour the slightly cooled brine into the jars, just covering the onions, while still leaving a ½-inch of space to the rim of the jar. Gently tap the jars against the counter to remove any air bubbles. Top off with more brine if needed and screw the lids on tight.
Let the jars cool to room temperature and then store the pickles in the fridge. These will taste good after about 24 hours, but get even better after a few days. Enjoy for up to one month! Eat up, Mama!