Place the onion on the cutting board and cut the end that is not the one with the stem, so that the onion has a flat bottom.
Turn the onion on the cutting board with the stem facing up and the flat bottom is down on the cutting board.
Take the knife and cut down into the onion, directly through the stem so that there are two halves.
Remove the outer layer of papery skin from each half, leaving the stem intact.
Lay one of the onions halves on the cutting board, so that the center of the onion (that you just cut through) is facing down.
Turn the knife sideways and cut in toward the stem starting on the lower part of the onion and working your way up at whatever thickness you want the onion pieces to be. Make sure to stop when you get close to the stem (the stem holds it all together).
Now slice down into the onion working your way from one side to another- the tip of your knife should be facing the stem but not cutting through it. Once again slicing to whatever thickness you want your final pieces to be.
Now slice through the onion in the opposite direction starting on the side that's farthest from the onion and working your way in toward the stem. The pieces of onion will fall as you cut.
Notes
Raw onions will last up to 5 days covered in the refrigerator.You can easily vary your cuts to whatever size onions you need.