How to Cut an Onion

Most people butcher onions like they’re in a horror movie. But once you know the right way to cut an onion, everything changes. You’ll save time, get cleaner cuts, and maybe even feel like you know what you’re doing in the kitchen.

Whether you’re tired of crying through meal prep or just want to stop mangling your knife, this guide walks you through everything you need to know: what knife to use, how to hold it, and the difference between a julienne and a half moon.

Why are you crying while cutting onions

If your eyes water every time you chop an onion, your knife is probably too dull.
A dull knife crushes the onion’s cells instead of slicing cleanly, releasing more of that tear-inducing compound into the air.

Here’s the fix: hone your knife before each use, keep your blades clean, and don’t let onion juice sit on your knife because it’s acidic and will dull it faster. A sharp knife won’t just save your eyes, it makes every cut easier and cleaner. If this isn’t enough, it’s time to sharpen your knives.

What knife to use

The right knife makes all the difference. You want something long enough to cut through the onion in one motion and tall enough to keep your knuckles off the board. A thinner spine helps with control since onions don’t need a heavy-duty blade.

Your best options:

• Chef’s knife
• Santoku
• Nakiri

If you want to geek out on blade geometry, check out our post on choosing the right knife for your kitchen. Otherwise, just stick to one of the suggested knives and you’ll be just fine. 

Anatomy of onion

Before you can master cutting an onion, it helps to actually understand what you’re looking at. Luckily, onions are simple little things once you break them down. There are three main parts you need to know: the stem, the root, and the grain.

The stem is the top of the onion – the part that would have been above ground as it grew. It usually comes to a slight point and is covered in papery skin. On the opposite end is the root, the fuzzy part that sometimes still has small root hairs or a bit of dirt on it. Unlike the stem, the root doesn’t have that dry outer layer, and it’s what keeps all the onion layers connected while you slice.

The grain runs from root to stem, creating natural lines through the onion. Understanding how that grain runs is key to controlling your cuts and the texture of your final dish. Once you can identify these parts, you’ve already taken the first step toward cutting an onion like a pro.

Julien vs half moon

At first glance, a julienne and a half moon cut might look the same, but they’re actually quite different. The difference comes down to the grain of the onion and how that affects the texture once it’s cooked.

A julienne cut follows the natural grain of the onion, running from root to stem. This gives you longer strands that hold their shape through the cooking process. Julienne cuts are great for dishes like caramelized onions or French onion soup, where you want the pieces to stay distinct and add a little texture.

A half moon cut, on the other hand, goes against the grain. This creates slices that soften and break down faster during cooking. Half moons are perfect for soups, sauces, or raw applications where you want a bit of onion flavor without long stringy pieces.

When deciding which cut to use, think about the final dish and the texture you’re going for. If you want structure and bite, go with a julienne. If you want smoothness and subtle onion flavor, choose a half moon. And if you’re not sure? Try both. Cooking is about experimenting and finding what works best for you.

Types of onion cuts

Onion rings

The easiest of the ways to cut an onion. Used mainly in making deep fried union rings, however there are other uses as well.

To cut an onion into rings simply:

1. Cup the stem off the onion and remove the skin
2. Chop large rings against the grain of the onion making 2-3 cuts
3. Separate the slices into individual rings
4. Enjoy 

Half moons

Half moons are another simple way to prepare your onion. 

Used when you want long strips of onion that do not stay together super strongly. Uses include slices for cheeseburgers or hot dogs, salads, stews and sauces where you want to onion to almost dissolve into the sauce

How to cut half moons

1. Remove stem of onion
2. Slice onion in half through root 
3. Remove skin of onion
4. Slice onion against grain as thin as desired
5. Enjoy

Julien 

Julien onions are easy to mistake with half moons but there are important differences. While the general shape is similar their uses are very different. As discussed before, Julien cut is used when you want the onion to maintain its structural integrity through the cooking process. Uses include carmalized onions and stews where you want the onion to maintain its structural integrity. 

How to cut Julien

1. Remove stem of onion
2. Slice onion in half through root 
3. Remove the root of the halves 
4. Remove skin of onion
5. Slice onion with the grain
6. Enjoy

Rough chop

A rough chop is the beginning of the fun when it comes to cutting an onion. This cut is very cost efficient as it uses nearly the entire onion, there is little to no waste. This cut is very versatile and is a very similar process to the dice and mince that we will discuss later. Uses include blended sauces, rustic style recipes anything going into a food processor. 

How to rough chop an onion

1. Remove stem of onion
2. Slice onion in half through root
3. Remove skin of onion
4. Place slices with grain of onion without cutting through completely, approx. 3/8 inch wide (strips should still be attached to the root)
5. Place a horizontal slice halfway up the onion without cutting through completely
6. Slice onion against grain approx. 3/8 inch cuts to stem
7. When the onion gets too thin to slice again, tip onion onto the face of the last cut. Proceed to place slices until you get to the stem
8. Chop the remaining onion that’s adjacent to the stem
9. Enjoy

Diced 

Diced onion is probably the most common use of an onion. While it works great on nearly every application most people look like they are playing wack-a-mole with their knife. Here is how to truly chop an onion the correct way. Uses include salsas, salads, sauces and sautéed onions

How to dice an onion

1. Remove stem of onion
2. Slice onion in half through root
3. Remove skin of onion
4. Place slices with grain of onion without cutting through completely, approx. ¼ inch wide (strips should still be attached to the root)
5. Place 2 horizontal slice halfway up the onion without cutting through completely
6. Slice onion against grain approx. 1/4 inch cuts to stem
7. When the onion gets too thin to slice again, tip onion onto the face of the last cut. Proceed to place slices until you get to the stem
8. Chop the remaining onion that’s adjacent to the stem
9. Enjoy

Fine dice

Fine diced onion is a true test of your knifework skill. While the process is the same as a rough chop and dice, the care and precision needed is increased. Showing off a quality fine dice will impress all your guests and make your meals worthy of being posted. Uses include garnish, burgers, salsas, chimichurris, salads.

1. Remove stem of onion
2. Slice onion in half through root
3. Remove skin of onion
4. Place slices with grain of onion without cutting through completely, approx. 1/8 inch wide (strips should still be attached to the root)
5. Place 3 horizontal slice halfway up the onion without cutting through completely
6. Slice onion against grain approx. 1/8 inch cuts to stem
7. When the onion gets too thin to slice again, tip onion onto the face of the last cut. Proceed to place slices until you get to the stem
8. Chop the remaining onion that’s adjacent to the stem
9. Enjoy and feel superior to your friends

Paste

Onion past is used when you want zero structural integrity with your cooking. While this can be achieved with a blender or even a food processor, where is the fun in that? We are here to learn how to prep our onions with our hands and a knife, no fancy machines. Uses include smooth sauces, spreads, foods requiring a very specific texture.

1. Remove stem of onion
2. Slice onion in half through root
3. Remove skin of onion
4. Place slices with grain of onion without cutting through completely as thin as possible (strips should still be attached to the root)
5. Place 3 horizontal slice halfway up the onion without cutting through completely
6. Slice onion against grain as thing as possible
7. When the onion gets too thin to slice again, tip onion onto the face of the last cut. Proceed to place slices until you get to the stem
8. Chop the remaining onion that’s adjacent to the stem
9. Press the flat of your knife against the onion and drag across your cutting board to pulverize the onion into a paste
10. Continue till all onion is in a paste
11. Enjoy 

Brunoise

If you want to take your knife skills and presentation to the next level, the brunoise cut is the way to do it. This technique separates the individual layers of the onion to create perfectly uniform cubes, just like you’d see in a professional kitchen. When done correctly, each piece is clean, precise, and identical in size.

The fine dice method described earlier works well for most recipes, but the brunoise adds an extra level of refinement. It’s commonly used for garnishes, pan sauces, salsas, chimichurris, salads, and other dishes where presentation matters.

While it isn’t essential for everyday cooking, mastering the brunoise is a great way to build control and consistency with your knife. Small details like this can make your food look and feel restaurant-quality.

1. Remove stem of onion
2. Slice onion in half through root
3. Remove root of onion halves
4. Remove skin of onion
5. Separate individual layers of the onion
6. Place cut with grain the same thickness as the layer of onion
7. Slice against the grain of the Julien strips the same thickness
8. Repeat on all layers of the onion
9. Enjoy your onion perfection 

Please enjoy and keep cooking!