 Three proven ways to cut an onion without crying. Peel the onion cut it in half and put it in the fridge for 30 minutes. Soaking it in a bowl of ice water works too. The more airflow, the better. It'll disperse the irritating onion gas before it hits those tear ducts. But whatever you do, make sure you're using a sharp knife. Instead of nice clean slices, you're basically smashing it, releasing more of the chemicals. And you may be asking, why are onions this way in the first place? Well, since they grow underground, it's their defense mechanism to protect them from those pesky and hungry animals.