How To Caramelize Onions: 4 Easy Methods

Caramelized onions are among my favourite foods. They’re one of the ultimate comfort flavours whether you’re adding them to a dish or eating them by the spoonful. Any of you who have caramelized onions at home knows one thing is true: These little beauties refuse to be rushed. If you want that umami-packed, mouth-watering flavour, then you need time—and there’s no substitute for it.

Since onions have a high concentration of water and sugar, the key to caramelizing them is to make sure these are both released at a slow and steady rate. As the onions are gently warmed they begin to sweat. The water is released first, then the sugars. The water then evaporates, allowing the heat to caramelize.

Some tricks and tips call for adding balsamic vinegar or brown sugar to the onions.  These additions may make the onions appear caramelized, but you will notice the difference in the taste. So for me, that’s a no-no. (Also, the onions themselves contain more than enough sugar to caramelize.)

Related: Types Of Onions And How To Use Them

So are there really four ways to make caramelized onions? Well, not really, because you will always need onions, fat and time. But, there are different methods of achieving the same result. By cooking them on the stovetop, in the oven, on the grill or in the slow cooker. Before we start, here are a few tips to keep in mind:

Don’t cut the onions paper thin

They will burn before they have a chance to caramelize; a good width to aim for is 1/8-in.

Avoid using a non-stick pan

You want the ooey-gooey goodness that is developed as the caramel adheres to the pan. You won’t get that with non-stick.

Deglaze the pan

Doing this with a tablespoon or two of water at the very end of the cooking process will release all the flavour. Cook, stirring until that water has evaporated, the onions are coated and the pan is clean.

Oil can be used instead of butter

I like butter for the flavour and it works because the onions are cooked at such a low heat, but oil will do the job as well.

4 Methods for Caramelizing Onions

1. On your stovetop

Peel and cut 2 onions into 1/8-in. slices;  you will have about 4 cups. Heat a 12-in. skillet on low. Add 2 tbsp butter or enough to coat the bottom of the pan. When butter has melted, add onions and stir to coat. Cook for 5 min. Stir and repeat for 40 min. or until onions are sweet, deep golden brown and very tender. Add another tbsp of butter if the onions appear dry. Season with salt to taste.

2. In your oven

This is my favourite way of caramelizing onions when I want to do a big batch. Why? Because you don’t want to overcrowd a skillet when cooking on the stovetop. If you do, the onions will release their sugars and water at different rates (bottom first), interfering with the uniformity of the caramelizing. So instead, try the oven: Preheat the oven to 300F. Peel and cut 4 onions into 1/8-in. slices; you will have about 8 cups. Spread the onions over a large baking sheet. Drizzle with 1/4 cup vegetable oil or melted butter and toss to coat. Transfer to the oven and cook for 10 min. Stir, then continue baking, stirring every 5 to 10 min for an hour or until onions are sweet, deep golden brown and very tender. Season with salt to taste.

3. On the grill

This method yields delicious caramelized onions with an added a hint of smokiness. One caveat: The heat of a BBQ tends to rise quickly so you do need to keep an eye out, lifting the lid as needed keep the heat down. You also must use a cast-iron pan. Preheat BBQ to low, about 300F. Peel and cut 2 onions into 1/8-in. slices; you will have about 4 cups. Place a 12-in. cast-iron skillet on the grill. Add 2 tbsp butter or enough to coat the bottom of the pan. When butter has melted, add onions and stir to coat. Cook for 5 min. Stir and repeat for 40 min. or until onions are sweet, deep golden brown and very tender. Add another tbsp butter if the onions appear dry. Season with salt to taste.

4. In a slow cooker

Peel and cut 2 onions into 1/8-in. slices; you will have about 4 cups. Combine onions, 2 tbsp oil and 2 tbsp butter in a 4- to 6-quart slow cooker. Cover and cook on low for 8 hrs or until deep golden, stirring once or twice.

How to use caramelized onions

In a dip Get our Caramelized Onion Dip With Sweet Onions And Crispy Shallots Recipe.

In pasta Get our Slow Cooker Caramelized Onion Pasta Carbonara recipe.

On pizza Get our Alsatian Pizza With Bacon and Caramelized Onions recipe.

Originally published in 2015; updated in 2023.