How to chop an onion
Chopping is probably the most common way to prep an onion. Chopped onions show up in anything that needs the basic, earthy pungent flavor that onions give. Chop them larger for longer-cooking dishes like stews and rustic soups, and smaller (call it a dice if you like) for anything from salsas to sauces to ragouts.
To start, cut the onion in half through the root. The root itself will help keep the onion together for chopping
Rotate the onion 90 degrees and cut off the papery end (not the root end). This will make the skin easy to peel away and discard.
Peel back the onion's papery skin. It's often easiest to peel away the first layer of the onion along with the skin.
Make a series of diagonal cuts (roughly 45 degrees) into the side of the onion. Keep more space between the slices for a large chop. Make the cuts closer together for a small chop or a dice.
Now make a series of horizontal cuts to finish shaping the chop or dice.
Finally, rotate the onion again and slice crosswise against the checkerboard pattern you made in the onion. The chopped pieces will fall away from the onion.