How to Make Caramelized Onions

Co-authored by Jessica Gibson

Last Updated: November 17, 2020 References Tested

Caramelizing onions is a simple trick that great cooks use to add tons of flavor to a dish. Start by slicing onions thinly and cook them for a long time over low heat with a little butter. The onions will break down and become sweeter the longer they cook, so take your time with making them. Then stir them into your favorite dip, pasta, or soup.

Ingredients

2 large yellow onions [about 1 pound (450 g)], peeled
2 tablespoons (28 g) of unsalted butter
Kosher salt to taste

Makes about 1/2 cup (97 g)

Method 1

Method 1 of 2:

Caramelizing Onions on the Stove

1
Cut 2 onions into thin slices. Place 2 peeled onions on a cutting board and cut each in half through the root end. Trim ¹⁄₂ inch (1.3 cm) off of the stem ends. Then lay the flat sides of the onions against the board and use a sharp knife to carefully cut the onion into ¹⁄₄ to ¹⁄₈ inch (0.64 to 0.32 cm) thick slices. Take care not to cut through the root end so the onion stays together as you cut. Once you've finished slicing across the onion, trim off the root end.^{[1]
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- Use your favorite type of onion. For example, caramelize red, Spanish, or Vidalia onions.
2
Heat the butter in a skillet until it sizzles. Put a deep skillet on the stove and put 2 tablespoons (28 g) of unsalted butter into it. Turn the burner to medium and leave the butter to melt. Let it continue to cook until it begins to sizzle a little.^{[2]
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- It's important to use a skillet with deep sides so the onions don't spatter or flip out of the pan when you stir.
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3
Put the sliced onions into the skillet gradually and add a pinch of salt. Put 1 handful of the sliced onions into the skillet and let them soften for about 1 minute. Continue to add the onions in handfuls, letting them soften a little so it's easier to stir them in the skillet. Once you've added all of the sliced onions, stir in a pinch of kosher salt.^{[3]
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- If you dump all of the sliced onions into the skillet at once, it will be difficult to stir and the onions on the bottom will cook faster than the ones on top.
- If you're only caramelizing 1 onion, you can probably put all of the slices into the skillet at once.
Did You Know? Although you can roast the prepared onions on a baking sheet, you'll still need to stir them frequently. They're also more likely to dry out and burn around the edges.
4
Cook the onions for 15 to 20 minutes for lightly caramelized onions. Turn the burner down to medium-low and stir the onions every 2 to 3 minutes for at least 15 minutes. The onions should turn a light brown color and you can turn off the burner if you'd like to leave the onions lightly caramelized.^{[4]
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- Use lightly caramelized onions for classic French onion soup or continue cooking them for softer, richer onions.
5
Sauté the onions for 15 to 30 more minutes if you want darker onions. To make softer, sweeter caramelized onions, continue to stir the onions frequently and cook them until they're a rich, golden brown. This will take between 15 and 30 more minutes for a total cooking time of 30 to 50 minutes.^{[5]
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- If the onions start to stick to the skillet, stir in 2 tablespoons (30 ml) of water or vegetable stock to loosen them.
6
Use the caramelized onions in dips, pasta, or eggs. Stir some of the hot, caramelized onions into scrambled eggs or pasta, such as carbonara. If you want to make a caramelized onion dip or spread, let them cool before blending them with sour cream and spices.^{[6]
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- To store leftover caramelized onions, put them into an airtight container and refrigerate them for up to 1 week.

Method 2

Method 2 of 2:

Trying Variations

1
Stir in balsamic and brown sugar for a richer flavor. Taste the onions after they're almost done caramelizing and decide if you want a slightly sweeter flavor. If you do, stir in 1 tablespoon (12 g) of brown sugar and 2 teaspoons (9.9 ml) of balsamic vinegar. Then finish cooking the onions until they're soft and caramelized.^{[7]
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- If you don't have brown sugar, substitute granulated sugar and add 1 teaspoon (4.9 ml) of molasses.
2
Simmer the onions in beer or cider to create thicker caramelized onions. If you'll be serving the caramelized onions with sausages or a roast, consider adding 1 cup (240 ml) of beer or cider to the onions after they've cooked for about 10 minutes. Bring the liquid to a boil and then turn the burner down so the onions simmer in it for about 20 more minutes.^{[8]
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- The beer or cider should evaporate once the onions finish caramelizing.
3
Stir in a pinch of baking soda to speed up caramelization. If you don't have the time to slowly caramelize onions, add a pinch of baking soda to the sliced onions when you add them to the skillet. The baking soda will raise the pH of the onions so they turn brown faster.^{[9]
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- Plan on using about 1/4 teaspoon (1.5 g) of baking soda for every 1 pound (450 g) of onion.
4
Add thyme for a slight herbal flavor. Get out 1 sprig of fresh thyme for each onion you're caramelizing. Pull off the leaves and add them to the skillet when you put the onions in. Stir to incorporate the herbs and finish caramelizing the onions.^{[10]
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- Use your favorite herbs for a different flavor. For example, chop fresh rosemary or sage leaves.
5
Caramelize the onions in a slow cooker for a hands-off method. Fill your slow cooker at least 1/2 full with sliced onions and add 1 tablespoon (15 ml) of olive oil or butter for every 1 pound (450 g) of onions. Put the lid on the cooker and turn it to low. Slow-cook the onions for 10 hours so the onions brown and soften.^{[11]
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- If you remember, you can stir the onions occasionally to help them cook evenly, but it's fine if you simply leave them to cook without stirring.
Tip: If you'd like thicker, richer caramelized onions, prop the lid of the slow cooker open and cook the onions for 3 to 5 more hours.

Community Q&A

Question

What type of brown sugar do I use?

Community Answer

Dark brown sugar would be best, but you can use any kind of brown sugar.
Question

Can I use coconut oil in a crock pot?

Community Answer

Yes, coconut oil can be used in a crock pot.
Question

How long do the slow-cooked onions keep in the refrigerator?

Community Answer

About a week, provided you remove excess liquid and properly store in an airtight container.