If I had to name a single fundamental cooking skill one must learn to become a better cook it would be, hands down, how to properly cut an onion.  Yes, there is a right and a wrong way to do this and once you learn the right way your life will become so much easier; well, easier at least when you are standing at your cutting board.

One of the benefits of cutting an onion this way is that all of the pieces are uniform and will therefore cook at the same rate.  This thinking can be carried through with all ingredients (peppers, garlic, chicken breast); by getting all the pieces of one ingredient to uniform size you can ensure a more consistent cook and a better dish.

The key to cutting an onion properly is LEAVE THE BASE ON.  Under no circumstances should you cut the base off until the end of the chop. I am not kidding.

Follow These Steps

1. Cut the top, then slice in half: Using a sharp chef’s knife, slice about a half an inch off the top of the onion and discard. Turn the onion to rest on this flat end and slice in half vertically.Tip: If you’re only using half of the onion, leave the skin on and wrap what you’re not using in plastic wrap.
2. Peel off the papery layers: Remove and discard the skin.
3. Chop vertically: Take one onion half and lay it flat on your cutting board. Holding the root end, carefully cut vertically, making sure not to slice all the way through. Tip: Leave the root side intact to make chopping easier.
4. Chop horizontally: Rotate the onion and slice vertically down through the onion, still leaving the root end intact. Discard the root end and repeat with the remaining half of the onion.

   

   Tip: The closer together the initial horizontal and vertical cuts are, the smaller the dice.

    

   (instructions taken from http://www.realsimple.com)