Welcome to my kitchen, and to a brand new series called “In The Kitchen.” This new series will be covering basic cooking techniques, knife skills and kitchen hacks to help make cooking from scratch easier for you. On my very first day of culinary school, the head chef of the school taught us how to dice an onion, so I thought it only appropriate for us to start this new year and this new series with the most fundamental cooking skill of all: how to cut, dice and slice an onion. Plus I also have step-by-step photos showing the best way to slice an onion.

a colander with onions, a bowl of diced onion

Have I ever told you the story about when I was a personal chef, the time I turned away an otherwise perfect client because they told me the didn’t eat onions? I told them I HAD to cook with onions and it was a deal breaker for me. That’s how important I think onions are to cooking. If you agree, then you’ll want to read on to learn the BEST way to slice an onion, and the proper way to dice an onion.

a yellow onion

What is the difference between chopped and diced onion?

The difference between chopped and diced is that chopped is looser. There may be some uneven pieces. Dice is ideally small squares of even sizes. Since there are layers to an onion, even an onion that is properly diced will fall apart into sheets, so they will not be cubes (the way diced carrots would stay cubed.)


How to Cut an Onion

Whether or not you are slicing or dicing your onion, this is the first part of the process. This technique will keep dirt and onion skin from getting onto your cut onion, and it is the safest method.

remove skin from onion
  1. Remove any very loose papery pieces of onion skin. remove onion root end
  2. Hold the onion on its side with root-end facing toward knife. Press the onion into the cutting board for maximum stability while removing root. Carefully cut root end off with a sharp Chef’s knife, leaving the core of the root intact. Remove the stem end of the onion
  3. Rotate the onion around, and cut off the stem end, just enough so that when you look at the cut surface of the onion, you have cut away any papery skin in the center of the cut end. Cut the onion through the stem and root end
  4. Placing the onion on one cut side, Cut through the center of the root and stem end of the onion to divide it into two equal halves. remove the skin and outermost layer of onion
  5. Remove the brown papery skin and first layer of onion from the outside of each half. This outer most layer of onion is actually more tough than the layers underneath, and it won’t break down as much when you cook it. That makes it unpleasant to eat.Now is the best time to clear off your cutting board. If there is any dirt on your board, rinse it off. For maximum stability, lay onion cut-side-down on work surface
  6. Lay onion cut side down on the work surface.

How to Dice an Onion Step-By-Step

Slice onion into slabs stopping just before you get to the root end. The root end will hold the onion together as you slice it.
  1. Leave root core intact to dice the onion. If right handed, place onion half, cut-side down with root end facing left hand. Hold chef’s knife in right and parallel to the cutting board. With left hand held flat on top of the onion, pressing firmly, slice into the onion, at desired thickness (about ¼-inch above the cutting board) from stem end toward root end, stopping just before the root is reached. Repeat at even intervals (about ¼-inch apart) through entire onion. Slice the onion, with knife tip stopping just short of the root end into equally thick slices.
  2. Rotate onion so the root end is facing away from you. Slice at even intervals (about ¼-inch apart), stopping the knife tip just short of the root core, with knife perpendicular to the cutting surface (or at a slight angle toward the center axis of the onion.)  dicing Onion
  3. Turn onion to original orientation, so root end is facing your left hand and stem end is facing your left hand. Cut knife through the cut end of the onion, slicing off onion dices as you go. Work all the way to the root end. Cut around the root end to use all edible parts of the the onion and limit waste.
  4. Once you get to the area around the root where you did not slice through in the earlier steps, tip the root end piece over cut-side down and use knife  to cut around the core into dice-sized pieces. This will limit waste.
diced onion

For more information on onions including how to caramelize them, check out this Produce Spotlight, Ultimate Guide To Onions

What is a French Cut sliced onion?

French slice is when an onion is cut from root end to stem end into pieces that run the length of the onion. This is the preferred method for slicing onion for caramelizing. Benefits of cutting an onion in the French slice method, is that the cell structure will hold the shape of the slices even as it completely softens. They will not break down to mush when cooked for a long time. You will also end up with “c”-shaped slices that are uniformly long. It is more refined because the size of the strips are relatively consistent and will cook at the same rate and provide an even texture in the final dish.

sliced onions
Shown here: Philly Cut Onion on top and French Cut Onion on bottom. Notice the relatively consistent size of the pieces in the French-cut onion, versus the small and large pieces in the Philly Cut.

Philly Cut Onions, on the other hand, are cut into slices parallel to the equator of the onion. This is actually a term I made up, because there is no official culinary name for this type of onion cutting. But I think it is an important distinction, and being from Philly, I thought the name appropriate. This is the perferred method for making Philly cheesesteaks. When an onion is cut this way, the onion will break down more rapidly as it cooks which lends itself to fast cooking methods such as making a Philly cheesesteak on a flat top griddle. This is a method of slicing that is useful for more rustic dishes that require quick cooking time.

Philly Cut Onion
Philly Cut Onion

How to Slice an Onion

For sliced onion, remove the core of the onion before slicing
  1. For French Cut Sliced Onions:  Working one half at a time, use tip of Chef’s knife to cut out the root core making a triangle shape.
French cut sliced onion
French cut sliced onion

Cut with knife parallel to the onions root end to stem end, working with the knife slightly angled toward the center axis of the onion. Repeat with the second half.

How to Philly Cut an onion, a less refined way to slice an onion for quicker cooking, rustic recipes and when you want the onion to break down as it caramelizes.
Philly Cut Onion

ALTERNATIVELY, For Philly Cut Sliced Onions; Working one half at a time, use tip of Chef’s knife to cut out the root core, making a triangle shape.  Cut onion half crosswise into thin slices with knife blade parallel to the equator, starting at root or stem end and slicing to desired thickness across the onion.

Thanks so much for reading! If you are new here, you may want to sign up for my email newsletter to get a free weekly menu plan and the latest recipes right to your inbox. If you make this recipe, please come back and leave a star rating and review. I would love to hear what you thought!

Happy Cooking! ~Katie

clock clock iconcutlery cutlery iconflag flag iconfolder folder iconinstagram instagram iconpinterest pinterest iconfacebook facebook iconprint print iconsquares squares iconheart heart iconheart solid heart solid icon
dicing Onion

How to Dice Onion

  • Author: Katie
  • Total Time: 3 minutes
  • Yield: 1 1/2 cups onion 1x


Here are the steps to dice an onion



1 onion


  1. Cut off root end of the onion, leaving the root intact but removing the fine thread like roots and any dirt. Cut off stem end of onion. Cut onion in half root through stem. Remove outer layer of skin and any fibrous layer of onion. Clean cutting board.
  2. Lay onion cut side down with root end toward your non-dominant hand. Holding knife parallel to the cutting board, slide knife horizontally into the onion at 1/4-inch intervals (or larger if desired) almost to the root, but not through it.
  3. Turning knife so that it is perpendicular to the board, cut through the onion so the tip stops just short of the root end at 1/4-inch (or larger) intervals.
  4. Turn onion so that the cut end is facing your dominant hand, cut through the onion to create diced onion pieces that are square or cube like.
  • Prep Time: 3 minutes
  • Category: mise en place
  • Method: knife skills
  • Cuisine: all


  • Serving Size: 1/4 cup
  • Calories: 17 calories

Keywords: how to dice an onion