How To Thinly Slice an Onion

Cooking Lessons from The Kitchn

Given that the vast majority of dinners start with a pile of thinly-sliced onions on the cutting board, we here at The Kitchn feel it's worth taking the time to make sure your onion skills are on point. Confidence is everything when it comes to dinner, am I right?

Grab your favorite chefs knife and your onion goggles — I'm about to show you how to cut your onion like a kitchen ninja.

What We Mean By Thinly Sliced Onions

Recipes are annoyingly inconsistent when it comes to sliced onions. Some say "thinly-sliced" or "thin-cut," some say "julienned," while still others call for onions to be "french-cut." These all mean the same thing: long, thin slices of onions all the same size and length.

Think of the Onion as a Globe

Think of the onion as a globe with the root end as the South Pole and the top as the North Pole. Running from North Pole to South Pole, you have lines of longitude — once you peel the onion, you can actually see lines in the onion that look just like the longitude lines on a globe. Thanks, Mother Nature!

To thinly slice our onion, we want to cut along those lines of longitude, top to bottom. Trim off the tip and the root, cut the onion in half from pole to pole, and then slice each half radially, with your knife slightly angled toward the middle of the onion.

Sound tricky? Don't worry — this is one of those kitchen skills that's easier done than said. Look through the slideshow gallery of step-by-step photos, and see for yourself.

Why Bother Slicing Onions This Way?

If you're anything like me, it probably feels more intuitive to thinly slice the onion into rings or half-moons rather than along the lines of longitude like this. But besides making you feel like a proper chef, this way of slicing onions has a few surprising advantages over half-moon slices.

First off, these thinly-sliced onions are all roughly the same length. This makes the finished dish look a little more polished, and it also means they'll cook more evenly and finish cooking at the same time. These onions also have a better texture after cooking — they'll still have a bit of chew and bite, while rings or half-moons tend to have a softer, somewhat mushy texture.

Does it truly matter whether you cut an onion thin julienned sliced or into half-moons if the end result is still spaghetti sauce? Nah, probably not. You'll be happy with your homemade dinner either way. But does giving your onions a little extra TLC make you feel that much closer to kitchen mastery? Most definitely.

How To Cut An Onion Into Perfectly Thin Slices

What You Need

Onions, any kind

Sharp chefs knife
Cutting board


  1. Trim the top off the onion: Cut enough off the onion that you cut through all the papery outer layers and expose the onion rings.
  2. Trim off the root end (optional): I feel that cutting away the root end makes it a bit easier to cut very thin, very neat slices. Leave the root attached if you'd like a little more stability as you slice.
  3. Slice the onion in half: Stand the onion on one of the cut sides and slice it in half.
  4. Peel the papery onion skin from both halves.
  5. Lay one half on the counter, like a dome. Turn the onion so that you'll be slicing along the lines of longitude, from top end to root end.
  6. Beginning on one end, slice radially toward the center: Hold your knife at a slight angle and cut slightly inwards, toward the middle of the onion. The first few slices don't need to actually need to go all the way through to the very center of the; just work radially from the side to the center gradually increasing the angle of the cut as you work toward the center.
  7. When you reach the middle of the onion, stop and tip it over: This makes it easier to slice the other half of the onion without holding your knife at an awkward angle. Now you can cut this part of the onion the same way you cut the first part.
  8. Slice the rest of the onion as you did before. Be careful when you start to get to the middle so that your knife doesn't slip. Keep your fingers out of the way as best you can! (If you left the root end attached, cut it away once you're completely finished slicing the onion.)
  9. Repeat with the other half of the onion.

This post has been updated — first published February 2010.

(Image credits: Kelli Dunn)