The crying response to onion vapors has to do with your eyes, not your nose. Using a sharp knife, to reduce the tearing and bruising caused by a dull one, may help, as will refrigerating the onion ahead of time. Keeping your eyes closed will help, but you may lose a finger or two!
The only thing that actually helps is to take a sip of water and keep it in your mouth.
cut them underwater helps for me.