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How To Dice An Onion

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Bowls of diced red and white onions.

Onions are such an important kitchen staple that it’s hard to imagine cooking a good meal without them. They are usually the first building block of flavor in soups, stews, and sauces; they also add texture and color to salads and salad dressings.

You may have your own way of dicing onions, but are you doing it the safest and most efficient way? It makes sense to learn, as it will make your prep time in the kitchen go much faster.

To start, you’ll need a large chef’s knife and a cutting board.

onion and knife on cutting board

Cut the onion in half through the root.

onion cut in half

Peel the papery outer layer from the onion and, if the first layer of the onion is discolored or tough, peel that as well.

peeling papery skin

Lay half of the onion flat-side down on the cutting board with the root facing away from you. Use your palm to apply light pressure to the top of the onion.

Cut a number horizontal slices in the onion from the front to back taking care to not cut through the root (that helps to hold the onion together). The number of slices you make will depend on the size of the onion and how large or small you want the dice to be.

making horizontal slices

With your hand on top of the onion and the point of your knife pointing at the root, make several vertical slices through the onion, being careful not to cut through the root.

making vertical slices

Rotate the onion and put your fingertips on top of it. Slice downward across the vertical cuts you’ve just made in the onion. After each slice, move your fingers closer to the root and keep slicing until you reach the root. Always keep your fingertips tucked under your knuckles so you don’t accidentally slice them.

Person cutting an onion lying on its side.

If you want the onion diced more finely, gather all of the pieces into a pile, and cut through them using a rocking motion with your knife.

making smaller dice

Repeat the process with the other half.

Note:  If you’re using raw onions in a recipe, you can minimize the sharp raw onion taste by soaking them in cold water for about ten minutes. (If you’re a raw onion lover, feel free to skip this step.)

onions soaking in water

Drain the onions.

Diced red onion in a sieve.

How to dice an onion — Tips to keep in mind

  • Make sure that your chef’s knife is sharp. Not only will it make slicing the onion easier and safer, but it will also cut down on the tears and burning sensation in your eyes. If you’re looking for a good, versatile knife sharpener, this is the one I have. It’s a bit of an investment but will make any chopping you do quicker, safer, and easier.
  • To prolong their freshness, store your onions in a dark spot at room temperature.


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  • Jenn,

    You are my favorite food blogger. I know your recipes are always great and do not need modifying, however, I disagree on how you dice an onion.

    I know this is how it is taught, I have seen it taught in all sorts of circles.

    I use a different method that only requires cutting from two different directions, not three.
    I have seen this once done on a FoodNetwork chef compitition.

    Cut BOTH ends off.
    Slice the onion in half, as you do
    And peel it as you do.
    Lay the onion on the flat cut surface, on the cutting board.
    Now slice it from one cut end to another, parallel to the cut ends.
    The width of these slices help dictate the size of your dice.
    This takes practice of moving your pointer finger next to the blade as it cuts to keep the onion in one piece.

    Now. here is the key, use the natural segments of the onion as one of your cuts.

    With the onion laying flat on it’s cut side, and holding the slices together with your left hand, start with your knife (assuming you are right-handed) laying parallel with the cutting board, almost laying on the cutting board, slice into the onion, from the right.

    Then moving your knife up the curve, make another cut, as you continue moving up the curve, your knife moves more towards vertical to the cutting board so that at the halfway point through your knife is now cutting straight down, and as you continue around the knife starts moving to parallel to the cuttingboard again, this time from the left.

    The size of these cuts are the finish of the size of the dice you are looking for.

    This can be done very fast once learned

    • Good to know your technique — thanks for sharing!

    • This is how I learned to do it as well!

      • — Judy Mustard on July 14, 2022
      • Reply

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