Peel the onion and slice it in half vertically.
Take one onion half and lay it flat on a cutting board. Using a sharp knife, cut the onion lengthwise in strips. Make a horizontal cut in the middle. Remember to stop right before the root - if you don't cut it, the onion will stay together.
Dice the onion, holding it by the root. It's easy!
Take the other half of the vegetable, lay it flat on the board, and cut off the root.
Cut the onion in slices, moving the knife to the end. Strips ready!