Learn the best technique to cut an onion with this SheKnows how-to!br br br br br br br br br Onionbr 1. Cut off ½ an inch of the non-root side of the onionbr 2. Place cut side on the cutting board and cut in halfbr 3. Peel off outer dry layersbr 4. To dice: -hold onion half on the root side and carefully slice from the cut side to the root side all the way across the onion, then slice across working your way up to the root end.