How to Slice an Onion

How ToOnion

Step by step instructions on how to safely slice onions both lengthwise, and crosswise.

Photography Credit: Elise Bauer

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)

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

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.

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.

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.

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.


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.


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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14 Comments / Reviews

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  • Love your website

    To get the smell of onions off your fingers and hands, rub a stainless steel soup spoon or serving spoon over your skin under running cold water.

    Works in an instant.

  • Shirley Lindsey

    There is an old saying “Whistle while you cut up onions and they won’t burn your eyes”. The secret there is that if you whistle, you are blowing the onion fumes away.

  • Mark

    I use that method because it’s safer and is just as fast as the way professional chefs cut. The wide knife protects your fingers when you use the claw method. That’s where you shape your hand into a claw and your knuckles act as a guide for the knife. The knife never completely leaves the cutting board.
    It always makes me nervous when I see professional chefs cut an onion. The cut off only one end. The other end acts to hold the onion together. Then they draw the knife in towards their hand keeping the knife horizontal, parallel to the cutting board. I am always expecting they will slip and slice their fingers open. I learned at a young age to never draw a knife towards you. Always away from you!

  • Byron Bales

    Wanna stop crying when you slice onions? Simple. Squeeze an orange skin over the bridge of your nose, close to your eyes. No orange? Just use a dip from orange juice and press it close to your eyes, near the bridge. No idea why it works, but it does.

  • Tina

    The best way I was taught by a European friend of mine to get rid of onion smell on hands, was to wipe your hand with anything that is stainless steel. Some kitchen supply stores sell a stainless stone, but you can use your cutlery (spoon is safe). Seems to work well for me. Am about to try your recipe for French onion soup today. Read all the comments and am looking forward to it. I do not like onions in general, but soup is great. Plus being sick seems to make me crave it, as it seems other commenters have seemed to feel the same way, and said it made them feel better. Here’s to health the way God intended – from nature / natural.

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How to Slice an OnionHow to Slice an Onion