Onion being cut on board

How to cut an onion

Learn how to cut an onion with our expert tips and techniques. Master dicing, slicing and chopping with our simple video tutorial and try our top recipes

The humble onion can feel like a tricky one to master when it comes to preparation, but learning the correct way to cut one can be achieved by a few simple and effective tips. It’s one of the most important cooking skills to learn, because often soups, stews and sauces start simply with a chopped onion. Follow this guide on safe methods of preparation, then try our tastebud-tingling soups, tarts and classic comfort food. Need even more dinner inspiration? Check out our collection of the best ever onion recipes.

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What is the difference between chopped, diced and sliced?

Sliced onions on board with knife

Chopping refers to cutting something up with a knife. You can, for instance, ‘roughly’, ‘finely’ or ‘cross’ chop something without specifying the shape or size of the pieces.

Dicing is a specific type of chopping. It’s a method of cutting into squares or cubes. The neater and more regular your pieces of onion are, the less likely it is that they will catch and burn around the edges of your pan, and the more likely it is that they’ll fry evenly. 

Slicing refers to chopping something in one swift movement. This is usually used to cut larger pieces of something. 

Make sure you have tip-top kitchen kit for the job with our review of the best knives under £40 and our guide to the anatomy of a knife

What are the different ways to cut an onion? 

How to dice an onion (cubes)  

Onion being sliced

  • Cut it in half, leaving the root intact (the roots are going to hold the onion together until you make the final set of slices to form neat cubes). 
  • Make two or three horizontal cuts into the first onion half, cutting towards the roots but not through them. 
  • Cut down vertically, holding the onion together as you do so. Repeat both these sets of cuts with the other half of the onion. 
  • Turn the onion so that the root end is furthest from the knife and chop downwards with a slicing motion, moving towards the root to create finely diced pieces of onion. 

How to slice an onion 

  • Cut the top off the onion (the end that looks like a spout rather than the root end). 
  • Peel the skin away, discarding the brown layers until you’re left with two clean, yellow onion halves.
  • Thinly slice the onion.
  • Alternatively, turn the onion so that the root is pointing south and slice into half-moons against the grain. 

Slicing into rings

  • Slice the top off the onion and peel, keeping it whole. 
  • Hold it firmly on a chopping board and slice across into rings. 
  • Discard the root and stalk ends. 

Want a simple tutorial? Watch our technique video on how to cut an onion:

Our top 5 onion recipes

Whether you need a mouthwatering side dish, a stunning summer tart or the perfect gravy to finish off your Sunday roast, our onion recipes are tried, tested and delicious. 
 

1. Best ever onion rings


No one can resist a pile of golden, crispy onion rings, hot from the fryer. Our best ever onion rings are the ultimate accompaniment to a steak dinner with all the trimmings. Try soaking the onion slices in buttermilk before frying, it takes the raw edge off the flavour and makes them deliciously mellow.
 

2. French onion soup 


This deeply savoury soup is an instant classic. Our easy French onion soup is ideal for your next dinner party. Make sure you caramelise the onions to get a really rich flavour and tender texture. 
 

3. Onion gravy


A rich and flavourful onion gravy is the only thing that elevates a Sunday roast or toad-in-the-hole from good to sensational. This simple recipe uses beef stock, red wine and herbs to pack in plenty of flavour. 
 

4. Cheeseboard and onion tart


Our cheeseboard & onion tart uses up remnants that would otherwise go to waste, and the mix of punchy blue, creamy brie and cheddar work well together. This impressive looking centrepiece is deceptively easy to make and is guaranteed to please plenty of palates. 
 

5. Welsh onion cake


Take a Welsh classic to the next level with sharp, salty cheese and delicate leeks. Our comforting Welsh onion cake with caerphilly is bound to be a family favourite and uses just a handful of ingredients. 
 

Mastered this technique? Check out our other top cookery advice… 

How to cut pineapple
How to make icing sugar
How to cook buckwheat
How to make French toast

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What’s your favourite dish using onions? Leave a comment below…