How to Slice an Onion

When a recipe calls for sliced onions, you have a choice of how to slice them—lengthwise or crosswise. If you are cooking the onions, as for caramelizing them, slice them lengthwise, or from root to stem. That way they will hold their shape better during the cooking. Crosswise cut onions tend to fall apart when cooked. Alternatively, when you are adding raw onions to a salad, for example, slice them crosswise. They’ll be easier to eat, and they look pretty too!

Does cutting onions give you tears? When you cut an onion, it breaks open the onion’s cel walls which releases fumes that react with the water on the surface of your eyes to form sulphuric acid. This burns your eyes, which makes you create more tears. The best way to avoid this is to limit your exposure to the cut surfaces of the onion and to work quickly. Wipe the cutting board down with a sponge or towel as soon as you are finished. The method shown here for the onion cut lengthwise will help limit your exposure to the onion fumes that make your eyes hurt.

How to Slice an Onion

  • Prep time: 2 minutes

You can either slice an onion lengthwise, from stem to root, or crosswise. If you are slicing the onions to cook them, as for making caramelized onions, it's best to slice them lengthwise, or from stem to root. This way the onion holds its shape better during long cooking. To slice an onion to be used raw in a salad or a sandwich, you can halve it and then cut it crosswise, for pretty, half moon shapes, or you can keep the onion whole and slice it crosswise for onion rings.



  • 1 onion, any color—red, yellow, white


Method for Slicing an Onion from Stem to Root (for cooking)

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1 Cut off the stem end of the onion, by about 1/4 to 1/2 an inch.

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2 Cut off the roots, but keep the root end intact. An intact root end will help hold the onion together as you make the other cuts.

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3 Place the onion with the cut stem side down on the cutting board. This will stabilize the onion. Cut the onion in half through the root end.

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4 Peel back the onion skin and place the onion halves cut side down on the board. If you want, to help keep your cutting area tidy, peel off or cut off the onion skin from the root end.

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5 Cutting along the natural lines of the onion, make angled cuts into the onion, aimed at the center of the onion. Cut almost all the way, but not all the way, to the root. It will be easier to handle the onion while cutting if the root end stays intact. Space your cuts depending on how thick you want your onion slices to be. More cuts for thinner slices, fewer cuts for thicker slices.

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6 Cut a "V" in the root end to cut away the tough root end that is holding the onion slices together.



Method for Slicing an Onion Crosswise (for serving raw in salads or sandwiches)

1 Cut off the stem end, place the onion cut side down on the cutting board, cut it in half through the root, and peel back the skins as in steps 1 and 2 above. Do not remove the skins. Place the onion halves cut side down on the cutting board.

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2 Hold the onion firmly with one hand, with the fingers curled inward. With a sharp chef's knife in the other hand, place the side of the blade against the knuckles of your index and middle fingers. Use this as a guide as you make slices through the onion. The curled fingers will protect your fingertips from the knife while cutting the onion. When you get close to the root end, you can hold on to the peeled back skins as you make the final cuts in the onion.

Here's a tip for serving slice onions raw in a salad or sandwich: soak them in a little water with lemon juice or vinegar to remove the harsh bite of the onion!


Method for Slicing an Onion into Onion Rings


1 Cut off the stem end. Peel back the outer peel of the onion.

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2 With the peeled onion on its side, slice off a thin sliver from the side. Then place the onion on the cutting board with this thin sliver cut side down. This will stabilize the onion's position so as you slice the onion rings, the onion will not roll.


3 Curl your fingers inward as you grip the onion to protect your fingertips. Slice the onion in whatever thickness you desire.  If you wish separate the cut disks into separate onion rings.

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  1. doug kaiser

    What ya know…I finally find out HOW TO SLICE AN ONION ….. my daughter and I went to lunch and she ordered her Hamburger with grilled onion and so I took what was left over home with me. I ate my half of burger and then hers which she did not eat….she is pregnant……WOW grilled onion,,, what a flavor on a burger and I ate them cold out of the fridge. So I started to investigate grilling onion and how they are cut and ended up on your site…..THANK YOU SO MUCH for this eye opener. I am on Social Sec. and I eat onion sandwiches often…sometimes with cheese and some time all by them selves. Am going to practice slicing…so thanks for the tips.

    • Elise

      You’re very welcome Doug!

    • doug kaiser

      I noticed the knife you use is large…is that your standard knife you use as a chef or just for that cutting of the onion. It seems no matter how I cut an onion, I always mess it up. I have been buying chopped onion in a container and using it when I cook which is not often. I appreciate your quick answer and surprised….with a smile THANKS Elise.

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