Without peeling the onion, cut one end (not the root end) and then cut it in half along the lines.
2
Peel the onion.
3
Place the onion on the flat side and cut vertically following the lines; also, be careful not to cut the root, as it will help you chop the onion more easily.
4
Turn the onion and make crosswise cuts until you reach the root. Chop the onion as finely as you desire.