How Do You Slice Onions For Caramelizing [& What Are They?]

Slicing, dicing, and chopping onions are fundamental cooking skills that take time to master. There are many ways to prepare an onion for the pan, and choosing the correct cutting method is an integral part of the cooking process. One of the easiest and most rewarding ways to enjoy this humble allium is caramelized onions.

Slice the onion as thinly as possible to increase the surface area that comes into contact with the pan’s heat. Caramelization occurs when the onion’s cell walls break down, releasing water and sugars. As the sugars brown, they recombine into new molecules and flavor combinations.

how do you slice onions for carmelizing

This is the traditional way to make caramelized onions, as the thin slices cook quicker and more evenly. Thicker pieces may require slightly lower heat and take longer to reach the point of caramelization. Finely diced onions caramelize quickly, producing a smoother consistency than standard slices.

Different Ways To Slice Onions for Caramelizing

Differing onion-slicing techniques take varying amounts of time to prepare and cook. In addition, recipes often call for certain types of caramelized onion, depending on the end product. 

For example, curries and soups require the onions to be jam-like, while a straightforward side serving of caramelized onions calls for a more textured consistency. 

Here are a few ways to prepare onions for caramelizing:

The Best Way To Do Vertical Slices

  1. Trim the stem and root ends from the onion and remove all of the papery peel from the outside.
  2. Slice the onion down the middle from top to bottom.
  3. Take one half of the onion and place it flat side down.
  4. From one edge of the onion to the other, slice vertically from stem-end to root-end.
  5. Each slice should be as thin as possible.
  6. Do the same for the second half.

The onion slices should all be the same thickness using this technique. 

However, the different onion segments will be different sizes, meaning the smaller pieces will cook quicker than the larger ones. Vertical Slices are a quick and easy method of slicing if presentation isn’t the primary goal of the dish.

How To Achieve Radial Slices

  1. Trim and peel the onions as usual.
  2. Slice the onion vertically from the stem to the root end.
  3. Place one-half face down as before.
  4. Cut towards the onion’s core at a shallow angle instead of cutting vertically down, as with the Vertical Slices.
  5. Radially repeat these angled slices.
  6. Each wedge of onion should be as thin as possible.
  7. Repeat for the next onion half.

Imagine the face of a protractor as half of the onion. Each slice radiates from the center of the onion at about 15°, making each section very regular in size. 

This technique takes practice but is the most reliable way to get consistently sized slices.

A Good Method For Horizontal Slices

  1. Peel, trim, and halve the onions as usual.
  2. Take half an onion and place the flat side on the chopping board.
  3. Instead of slicing vertically (top-to-bottom), start slicing horizontally from one end to the other.
  4. Slice as thinly as possible.
  5. Repeat with the rest of the onions.

This slicing style produces onion ‘strings’ that retain their long, thin shape as they caramelize. This slicing method is quick and easy but leaves you with varying sizes of onion string. 

When cooking, more care is required as the smaller pieces will caramelize faster. However, the stringy consistency is excellent for onion chutney or relish.

The Easiest Way To Dice Onions

  1. After trimming, peeling, and halving the onion, place the half face down on the board.
  2. Start by slicing vertically from the root end to the stem end.
  3. Don’t cut all the way through the base of the root end as you make each slice.
  4. Once the slices have been made vertically, rotate the onion at 90° degrees.
  5. Now start slicing horizontally from the stem end, keeping each slice thin.
  6. Slice until you reach the root end.
  7. Finely chop the remaining root end piece.
  8. Repeat as needed.

When diced this way finely, the caramelization process will happen at a different rate than in larger slices. Therefore, caramelizing diced onions requires extra attention, as they will burn quickly if not watched closely. 

The end product will have the consistency of jam or other preserves.

How To Make Caramelized Onions

The key to perfect caramelized onions is time. The times given by almost every recipe vary wildly, from as short as five minutes to two hours. The level of caramelization will depend on how they are sliced and how long they cook.

Food scientists and amateur cooks have done various culinary tests to determine when onions have truly been caramelized. Their findings indicate that onions must be cooked at low heat (350°F or lower) for a long time to achieve peak caramelization. 

A good rule of thumb has also emerged – 15 minutes for ‘golden-brown’; 30 minutes for ‘caramelized’; and 60 minutes for a ‘jam-like’ consistency.

Here is a quick guide to perfect caramelized onions:

  1. Place a pan on the stovetop and bring it to medium heat.
  2. Slice the onions to the desired shape and thickness.
  3. Once the pan has reached temperature, add a tablespoon of oil, butter, or other cooking fat.
  4. Add the prepared onions to the pan and stir to coat them in the fat.
  5. Reduce the heat to low and allow the onions to cook gently.
  6. After five minutes, add half a teaspoon of salt and half a teaspoon of sugar and stir.
  7. Simmer the onions on low heat, occasionally stirring.
  8. If they start sticking, add a tablespoon of water and stir. Repeat as needed.
  9. Remove from the heat when desired caramelization is achieved.

The best way to tell when caramelized onions are done is to taste them as you go. 

Patience is vital as the sugars take time to break down and turn that unmistakable caramel color. As the sugars brown, they will take on different flavor characteristics, increasing the sweetness and richness.

Some shortcuts are floating around, such as adding a little baking soda to the onions while cooking. Doing this speeds up another reaction that can occur when cooking food called the Maillard reaction. 

The Maillard reaction and caramelization are two different methods, and accelerating the process doesn’t necessarily mean quicker caramelization.

Final Word

Onions have been a staple food in the human diet since the Stone Age, and we have found many inventive and creative ways to cook and eat them. But, as with anything, practice makes perfect, and slicing onions is no exception.

Caramelized onions are one of the most enjoyable ways to experience this versatile bulb and can add a little extra dimension to almost any dish.

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