How to Dice an Onion

Almost every savory recipe starts with a diced onion, so learning to cut one quickly and evenly saves you time nearly every night you cook. Evenly sized pieces also cook at the same rate, which means no burnt bits mixed with raw ones. The method below is the one professional cooks use, and it gets faster with practice.

Set Up Your Station

You need a sharp chef’s knife and a stable cutting board. Put a damp paper towel or thin kitchen towel under the board so it won’t slide. A sharp knife is actually safer than a dull one because it cuts cleanly instead of slipping off the onion’s slick surface.

Before you start, practice the claw grip: curl the fingertips of your guiding hand under, so your knuckles face the blade and your fingertips are tucked safely behind them. The flat of the knife can rest lightly against your knuckles as a guide.

Halve and Peel

1. Cut a thin slice off the stem end (the pointed top), leaving the hairy root end intact. The root holds the layers together while you cut.
2. Stand the onion on the flat end you just made and cut straight down through the root, splitting it in half.
3. Peel off the papery skin and the first tough layer if it looks dry or blemished.
4. Lay each half flat side down on the board, with the root end pointing away from your knife hand.

Make the Cuts

1. Vertical cuts: Using the tip of the knife, slice from just in front of the root to the cut end, keeping the root connected. Space the cuts about 1/4 inch apart for a small dice or 1/2 inch for a larger one.
2. Horizontal cuts (optional): Hold the top of the onion flat with your palm, keep your fingers raised, and make one or two horizontal cuts toward the root, again stopping short of it. Many cooks skip this step, since the onion’s natural layers already do much of the work.
3. Crosswise cuts: Using the claw grip, slice across the vertical cuts from the cut end toward the root. The onion falls into neat cubes.
4. When you reach the root, turn it on its side and chop any usable pieces, then discard the root.

Fewer Tears

Onions release irritating compounds when their cells are cut. A few things help reduce stinging eyes:

• Chill the onion in the fridge for 30 minutes before cutting.
• Use the sharpest knife you have, which crushes fewer cells.
• Work near a running range hood or an open window.
• Leave the root end for last, since it contains more of the irritants.

Storing and Final Tips

Whole onions keep best in a cool, dry, dark spot with good airflow, away from potatoes. Store cut onions in a sealed container in the fridge and use them within about a week. You can also freeze diced onions in a flat bag for cooking. Slow down until the motions feel natural; speed comes with practice, not effort.