I have a happy chopper from Tupperware, it's fantastic and the only way I chop an onion You put it in this container that has a blade in it, put the lid on and turn the lid and it dices up the onion perfectly.
I used to work for tupperware and I am the same, except I have now gotten rid of the happy chopper for the upgraded one (name I cant think of) it is so much easier to use!!! It has a drawstring instead of twist action and yep, no tears!!!

You are welcome to try my happy chopper if you like, its sitting in the cupboard unused. Pm me your address and ill send it off no cost