How To Cut An Onion

How to cut an onion is a question for the ages, says food blogger & photographer Ksenia Prints of At the Immigrant's Table. It's one of the first things chefs learn how to do in culinary school, and it's the subject of dozens of YouTube videos.

Everyone and their grandmother has the best advice on how to prevent yourself from crying while cutting an onion. You've been told a thousand and one times what the ultimate approach is to prevent an onion from slipping on the cutting board. You've bought goggles and kitchen onion cutting knick knacks, washed your onions and your knives, and just about given up on the whole thing. But you are still not anywhere closer to finally figuring out how to cut an onion.

Well, good thing we're here to make sense of this mess and to tell you once and for all how to cut an onion.

Should you wash onions before cutting them?

It is not necessary to wash an onion before cutting it. Most vegetables that have a peel are protected from the germs and microbes on the outside. Though some microbes will penetrate the onion as we slice it through the peel in the first cut, this is a very minor contamination. As we usually proceed to cook our onions, any foodborne illnesses that could have transferred from the peel will be cooked out.

If you are going to eat your onion raw, like in a salad or a burger, you may want to be more vigilant and rinse the onion first.

What part of onions makes people cry?

Onions produce a chemical irritant called syn-Propanethial-S-oxide. This chemical stimulates the lachrymal glands in our eyes, causing them to release tears. The part of the onion that holds this chemical is the core. Therefore, when people slice an onion into those beautiful thin rounds, they're actually cutting directly into the most tear-inducing part of the onion.

Cut onion in half

Take a sharp chef's knife, and cut the onion in half lengthwise. This means you will split the roots and the top of the onion in two.

Peel your onion

The next step is to peel your onion. Remove the skin and any areas of the onion that are looking slightly rotten or worse for wear. This rot sometimes happens to an onion that's been kept in a moist place, but it doesn't mean you need to throw the whole onion out. Just cut off the bad parts and proceed with the next steps.

We like to peel the onion after making that first cut in half, just because it makes it easier to hold onto the peel.

Cut off the root of the onion, but leave the top end intact

If you are going to dice your onion or cut it into strips, then proceed to cut off the roots of the onion on both sides, but leave the tops on both onion halves intact. This will give you something to hold onto as you cut the onion and will prevent the onion from slipping out and allowing you to accidentally nick your fingers.

Additionally, because the core of the onion contains the majority of the syn-Propanethial-S-oxide, getting rid of the root can help minimize the tears associated with cutting an onion.

Cut each onion half into strips

If you are going to dice your onion, then hold tightly onto the root part and leave a gap of about half an inch between your fingers and the root of the onion. Start cutting the onion into slices that go from the root and toward the top—that is, vertically. That way, you will always have an uncut part of the onion in your hands, and the strips shouldn't fully separate from the top.

The width of the slices will determine the final dice, so if you want to dice the onion finely, make the slices narrow, and vice versa. If you're looking for a small dice, cut each onion half into matchsticks of about a quarter of an inch thick. The sharper your knife is, the finer your dice can be. Once you've finished one half, move on to the second half and repeat the steps.

If your recipe calls for onion slivers or crescent moons, then instead of cutting the onion into vertical strips, slice it into horizontal strips. That way, you'll end up with very clear crescent moon-shaped onion slivers. You can stop once you complete this step—you just need to chop off the root and dispose of it.

Cut the strips into cubes

If you require a diced onion, then change the orientation of your knife and proceed to cut the slices you made crosswise into cubes. You can do so by simply turning the onion half, or turning your knife.

To dice the onion finely, cut the narrow onion strips into tiny cubes, each about an eighth of an inch. You can do so by keeping your knife very close to the cutting board and never fully lifting the chopping hand, just the wrist. You do not have to go lightning fast—that is how accidents happen! (Well, this and using dull knives. Please make sure your knives are sharp before attempting to dice an onion.)

How do you cut an onion without tears?

As we mentioned, the part of the onion that makes people cry is the core. Therefore, there is one good method to cut an onion without tears: You have to fully remove the root of the onion completely. You can do this by inserting a sharp paring knife and cutting around the root, thus ending up with a triangular shape that contains the onion's root and core. You can do this after cutting the onion in half as well, but it may cause a bit of tears from initially cutting the onion in half.

Another method is to rinse the onion's flesh and your knife after cutting it in half. This washes off some of the tear-inducing chemical, though it's not 100 percent foolproof.

How To Cut An Onion
4 from 1 ratings
Wondering how to cut an onion perfectly every time? We've got the tips and tricks to help you out without accidentally cutting yourself or crying.
Prep Time
1
minute
Cook Time
0
minutes
Servings
1
onion
diced onion
Ready in 1 minute
Ingredients
  • Onion
  • Sharp knife
  • Cutting board
Directions
  1. Cut onion in half.
  2. Peel onion. Wash under cold water, if desired.
  3. Cut off the root of the onion, but leave the top end intact. Repeat on both halves.
  4. Set one half aside, and lay the other side on the cutting board with the cut-side facing down. For a slivered onion, cut onion into horizontal, crosswise slices. Repeat with other half.
  5. To dice an onion, hold onto the top end of the onion. Leave a gap of about half an inch between your fingers and the knife. Start cutting the onion into slices that go from the root and toward the top—that is, vertically. That way, you will always have an uncut part of the onion in your hands, and the strips shouldn't fully separate from the top. Finally, cut the onion slices crosswise into a dice.
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