Caramelized Onions

Last updated: Jul 28, 2023 · Recipes developed by Vered DeLeeuw and nutritionally reviewed by Rachel Benight MS, RD · This website generates income via ads and uses cookies.

Caramelized onions are a delicacy. They take some time to cook, but the buttery, flavorful, almost sweet result is very much worth it.

You can use them to top a variety of dishes, and they keep in the fridge for several days, so your effort in making them will be well-rewarded!

Caramelized onions served on a white plate with a napkin.

The way onions are transformed by cooking is miraculous. Even cooking them for just a few minutes takes much of their sharpness away.

And when you patiently cook them in butter over low heat until they are caramelized, they become incredibly soft, buttery, and flavorful.

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Ingredients

Here’s a look at the ingredients you’ll need to make caramelized onions. The exact measurements are listed in the recipe card below.

Onions: In this recipe, we will use two large onions. I like to use yellow onions, but other onion varieties work too.
Butter: Whether salted or unsalted – I’ve used both, and they work equally well.
Salt: I use Diamond Crystal kosher salt almost exclusively in my recipes, including this one.

The ingredients needed to caramelize onions.

Onion Varieties

I typically use yellow onions in this recipe, but all onion varieties can be successfully caramelized.

You can use yellow, red, or white onions. White onions are sharper but still have enough natural sugars to become caramelized.

And you can definitely use sweet onions such as Vidalia, which are relatively high in natural sugars.

The onion varieties that can be caramelized.

Variations

You can cook the onions in olive oil instead of butter. However, I have found that cooking them in butter helps them to caramelize, thanks to the milk solids that become browned as they cook.
Adding a splash of balsamic vinegar promotes browning. It’s helpful in this caramelized shallots recipe. However, it’s not mandatory, and I rarely use it.
Although the onions are flavorful just as they are, you are welcome to season them. I sometimes add a pinch of garlic powder and smoked paprika. An advantage of the paprika is that it adds color in addition to a smoky flavor.

Caramelized Onions Instructions

Here’s an overview of the steps you’ll need to take to make this recipe. The detailed instructions are listed in the recipe card below.

Your first step is to peel the onions, rinse and dry them. Next, cut them into slices, and separate the slices into rings.

When cutting the onions, you’ll want to cut them in half through the root end, then position them with the root end facing you and slice them into ¼-inch slices.

Cutting an onion in half through the root end.

At this point, you’ll want to lower the heat to medium-low. Now starts the fun part: you’ll cook the onions for about 45 minutes if you want them truly caramelized.

Keep cooking the onions, stirring them often. If the pan becomes too hot and there are brown bits on its bottom, add a splash of water and use it to deglaze the pan. You can lower the heat to low if this keeps happening.

Adding water to the pan to deglaze the bottom.

After about 45 minutes, you’ll be rewarded with gorgeous, silky strands of well-browned onions. They will be very flavorful and completely lose their sharpness. In fact, they’ll be almost sweet.

The last stage of cooking the onions. They are now fully caramelized.

Expert Tip

There’s a difference between sauteing onions (browning them) and caramelizing them. In both cases, you cook the onions in fat – olive oil or butter.

But when sauteing them, you can cook them for a shorter time (around 15 minutes) over medium heat.

When you caramelize them, you cook them for much longer – as long as 45 minutes – over medium-low or even low heat.

The results are quite different, as you can see:

A four-photo collage showing cooking levels of onions: raw, blonde, browned, and caramelized.

Recipe FAQs

Can I use red onions?

Yes, you can caramelize red onions. In fact, all types of onions can be successfully caramelized – yellow, white, red, and sweet onions such as Vidalia.

Should I use oil or butter in this recipe?

I recommend using butter. Although oil works, too, the milk solids in butter help with the browning process, similar to the role they play when blackening food.

Should I add sugar?

There’s no need to add sugar. Onions contain natural sugars which promote the browning process.

Do you cook the onions covered or uncovered?

I leave the pan uncovered. Covering the pan will create steam. My goal is to brown the onions, not steam them.

Serving Suggestions

These onions make the perfect topping for so many dishes! Here are just a few:

Storing Leftovers

You can keep the leftover in the fridge, in an airtight container, for up to five days. Reheat them in the microwave, covered, at 50% power.

More Onion Recipes

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Recipe Card

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Caramelized onions are a delicacy. They take some time to cook, but the buttery, flavorful, almost sweet result is worth it!

Prep Time15 minutes

Cook Time45 minutes

Total Time1 hour

Course: Side Dish

Cuisine: American

Servings: 4 servings

Calories: 80kcal

Cook ModePrevent your screen from going dark

Instructions

Peel the onions, rinse, and dry them. Cut them in half through the root. Remove the root, then position them with the root end facing you and slice them into ¼-inch slices.
Heat the butter over medium heat in a large, deep skillet. Tilt the skillet to spread the butter over the bottom.
Once the butter starts foaming, add the onions in two or three batches, sprinkling salt on each batch and allowing it to slightly soften before adding the next batch.
Lower the heat to medium-low. Cook the onions, uncovered, stirring them often, until they are very soft and deeply browned. This should take a total of about 45 minutes. If the pan becomes too hot and there are brown bits on its bottom, add a splash of water and use it to deglaze the pan. You can keep adding water as needed or lower the heat to low.
Remove the caramelized onions to a plate. Serve immediately.

Notes

You can make this recipe with red onions if you wish. In fact, all types of onions can be successfully caramelized – yellow, white, red, and also sweet onions such as Vidalia.
Although oil works in this recipe, the milk solids in butter help with the browning process, similar to the role they play when blackening food.
There’s no need to add sugar. Onions contain natural sugars which promote the browning process.
You can keep the leftover in the fridge, in an airtight container, for up to five days. Reheat them in the microwave, covered, at 50% power.

Add Your Own Notes

Nutrition per Serving

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