How to Slice an Onion, a Step-by-Step Photo Tutorial

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Heather says:

Knife skills are important for every cook and this step-by-step photo tutorial illustrates how to slice an onion. With a little practice slicing onions becomes a quick chore and eliminates the temptation of the expensive pre-sliced onions in the produce department. Yay for self-sufficiency.

The right tools help. For this chore I prefer a chef knife1, but a utility knife1 can be used in a pinch. Ready?


Grab the onion, a knife, and a cutting board.

Cut off the tip

Slice the tip off of the onion.

Slice the onion in halfSlice the onion in half, through the root. Use the tips of your fingers to steady the onion.

Peel the onionPeel the top most layer from the onion. If the onion is bruised, sometimes a couple of layers will need to be removed.

Slice almost to the rootGrip the onion with the tips of your fingers. Work from the opposite side. Insert the tip of the knife close to, but not through the root. The root will stabilize the vegetable until it has been sliced. For best results try to keep the slices uniform in width, but please don’t break out a ruler. Having the slices uniform in thickness ensures the onion will cook evenly in a recipe.

Slice off the root Slice off the root of the onion. It’s more fun if you make kung-fu noises during this part.

AdmireAdmire your work, then break apart the piece.

Scattered OnionsAll done!


1 These are affiliate links. They are for knives I own and have used for over ten years. I particularly like the chef knife’s size for my hand. There are higher quality knives out there, but these are the ones I currently own and find useful.

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15 thoughts on “How to Slice an Onion, a Step-by-Step Photo Tutorial”

  1. I took a knife skills class a couple of years ago and it’s made my life much easier. A few good knife skills and a sharp knife can reduce your prep time dramatically. Good tutorial.

    • I helped teach a cooking class for our 4H club, and the lady who was the primary teacher said that cutting the root end is generally what causes the tears to start, so if you cut it in a way that you can leave that attached until you're nearly done, it should help.

      I'm also thinking that perhaps, since wearing contacts helps a lot to eliminating the onion tears, maybe some swimming goggles would do the same thing? Just a theory I came up with right this moment. If I had any goggles, I'd try it out now!

      • Yes! Goggles do help!

        I got a discount pair just to try it out, and wore them while I prepped a batch of french onion soup. When my wife called up the stairs to tell me to open a window because she was crying from the onions, I got the idea that the goggles might be working. 🙂

  2. Thanks, now I need that knife sharpening tutorial you promised recently! As for crying, one of my friends observed recently that if she's wearing her contacts she doesn't have a problem. So far I think she's right, and contacts are waaay more fashionable than those silly goggles they sell–one of the few perks of poor vision.

  3. After a bit of practice, you get fast enough at slicing/dicing onions so that you can do it without the crying/tears. After each onion, throw it into a covered container and move on to the next one. that way you keep the amount of exposed fume-releasing onions down to a minimum

    • I concur.

      I hear a lot of folk remedies, but not chopping onions in a confined space and doing it quickly are probably the best bets. Unless of course you want to break out the chem goggles.

  4. One thing I feel a tremendous need to share:

    If you get an idea to chop up a whole bunch of onions to have on hand in the fridge or freezer
    and if you think that using a food processor to do this would be a great idea
    think again.

    I did that once — ONCE! My freezer smelled like onions for over a year.

    If you're doing just enough for the recipe you're going to make, fine. But the food processor smashes up the cell walls and releases even more of the smelly stuff.

    For the same reason, be sure to use a VERY sharp knife when slicing/chopping the onions. A dull blade will tend to smash the cell walls rather than make clean cuts thru them.

    So, if you want to chop onions ahead of time to refrigerator or freeze, use a very sharp knife and store them in an airtight container – I use a mason (canning) jar and it works great.

    Hope that wasn't too confusing. I haven't had my coffee yet….

  5. I was always tempted to wear goggles when I worked in a professional kitchen. Unfortunately, they wouldn't let me, and I always had about 20 pounds of onions to cut every morning. Do you know how mad people get when you use those meat slicers to slice onions? In all fairness, they refused to give me an area to do prep, and I was running a very busy sandwich bar.

    • I used to do a lot of food prep (we all did) at my last job. One of our best sellers were massive, beer battered onion rings. I used to cut onions for hours. Having a fan at my back helped tremendously.

  6. Great tutorial, Heather!

    The only suggestion I would make is in the third photo, after the ends are cut off, I put the cut-side down. Then the onion really doesn't have any way to roll out from under the knife. 🙂

    • I leave the root intact to keep the onion together until I'm done, so laying the onion on its side provides a more uniform surface for the blade of the knife, if both ends were removed, I would agree completely. It's just a variation where we each have our own preference.


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