There are tons of ways to cut an onion, but after cooking for over 23 years I’ve found that there are really only four ways to cut an onion that can cover every dish you will ever need onions for (Julienne, dice, large chunks and onion rings).
No matter which way you want to cut an onion, you always start the same way by cutting off the top and bottom of the onion.
After you cut off the top and bottom, remove the outer brown/yellow skin. From this point on, the next step will depend on which cut you want to do. The most common cut is the traditional julienne cut (thin strips).
All you have to do is cut the onion in half (from top to bottom). From there turn the two halves so the newly exposed side is face down (as seen in the above image) then continue to cut thin strips so perpendicular to the top and bottom of the onion (parts you originally removed). This will create thin slices of onion that can be easily broken apart. This is the most common cut that is used in stir fry and grilled onions.
The second most used cut for onions is dicing an onion (making little square pieces). Going back to where your onion has the top and bottom removed as well as the skin, again you are going to cut the onion in half vertically. However, instead of cutting julienne cuts that are perpendicular to the top and bottom of the onion, you are now going to cut parallel cuts that are roughly 1 cm thick (as shown in the image above on the left side). Your cuts should almost look like half of an onion ring at this point, from there you will make a second round of cuts in a perpendicular direction to turn the half rings into diced square pieces (as shown in the image above on the right side). Diced onions are usually used in spaghetti sauce, salsa, chili, etc…
For the last two ways to cut an onion, if you go back to the whole onion that has the top, bottom and skin removed you will want cut the onion in half again but instead of cutting it vertically you want to cut it horizontally (as shown in the image above).
Now the third way to cut an onion is large chunks which you normally see on skewers or stir fry that have large pieces of pineapple, shrimp or chicken where you want the onion to be the same size as the chunk of meat (instead of a strip of meat which would probably be best paired with a julienne cut). Once you have the two halves separated, all you have to do is cut the onion like you would an eight sliced pizza pie (as shown in the image above).
The last way to cut an onion is probably the most famous way, which is the onion ring cut. This is obviously used for onion rings, but it is also used for burgers too. Like the large chunk cut, once the onion is free from having a top, bottom and skin you will cut the onion in half horizontally. From there, pick up one half and hold it vertically and carefully cut it down the middle (shown in the image above). Do that again to the other side and your are done. This is the easiest way to cut an onion but you have to be careful not to cut yourself. I hope this post helps for people that have never cut an onion before. Please remember to always cut onions in a well ventilated area because the sulfur from the onion will make you cry.