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    Home » Keto Side Dishes » Caramelized Onions

    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.

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    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.

    Jump to:
    • Ingredients
    • Onion Varieties
    • Variations
    • Caramelized Onions Instructions
    • Expert Tip
    • Recipe FAQs
    • Serving Suggestions
    • Storing Leftovers
    • More Onion Recipes
    • Recipe Card

    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.
    Slice an onion into ¼-inch slices.

    Now that the onions are ready, heat the butter in a large, deep skillet over medium heat. You want the skillet to be deep because this makes it easier to stir the onions without them flying into your stove!

    Tilt the skillet to spread the butter. Once the butter starts foaming, you'll want to add the onions in two or three batches, sprinkling salt on each batch and allowing it to slightly soften before adding the next batch.

    Adding butter to the skillet.
    Adding the onions to the skillet.
    Sprinkling the onions in the skillet with salt.

    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.

    Cooking the onions, stirring often.
    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:

    • Steak. Whether New York strip steak, ribeye steak, or picanha, these onions can enhance almost any type of steak you can think of. They are also delicious on top of lamb steak and cauliflower steak.
    • Liver. I like to add them to chicken livers or beef liver.
    • Hamburger. I use them as a topping for baked hamburgers, bison burgers, and turkey burgers.
    • Sandwiches. They take grilled cheese sandwiches to the next level!
    • Eggs. Add them to fluffy scrambled eggs and omelets like this egg white omelet. Want to be super indulgent? Top soft-scrambled eggs with a dollop of sour cream and some of these onions. Mmm good!
    • Vegetables. They greatly enhance mashed cauliflower, sauteed spinach, and roasted green beans. They're also great in this green bean casserole.

    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.

    Caramelized onions served on a white plate with a napkin.

    More Onion Recipes

    • Roasted red onions served in a white bowl.
      Roasted Red Onions
    • Onion soup is served in a white bowl with a spoon and a napkin.
      Onion Soup Recipe
    • Roasted onions served on a white plate.
      Roasted Onions
    • Pickled red onions in a sealed jar.
      Pickled Red Onions

    👩🏻‍🍳 I aim to publish a new recipe once or twice a month. Want these recipes in your inbox? Subscribe today! You can unsubscribe at any time.

    Recipe Card

    Caramelized onions served on a white plate with a napkin.
    5 from 25 votes
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    Caramelized Onions

    Caramelized onions are a delicacy. They take some time to cook, but the buttery, flavorful, almost sweet result is worth it!
    Prep Time15 minutes mins
    Cook Time45 minutes mins
    Total Time1 hour hr
    Course: Side Dish
    Cuisine: American
    Servings: 4 servings
    Calories: 80kcal
    Author: Vered DeLeeuw
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    Ingredients

    • 2 large yellow onions
    • 2 tablespoons butter
    • 1 teaspoon Diamond Crystal kosher salt

    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.

    Video

    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.

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    Nutrition per Serving

    Serving: 0.25cup | Calories: 80kcal | Carbohydrates: 7g | Protein: 1g | Fat: 6g | Saturated Fat: 4g | Sodium: 328mg | Fiber: 1g | Sugar: 3g
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    DisclaimersMost of our recipes are low-carb (or keto) and gluten-free, but some are not. Please verify that a recipe fits your needs before using it. Recommended and linked products are not guaranteed to be gluten-free. Nutrition info is approximate, and the carb count excludes non-nutritive sweeteners. Nutrition info may contain errors, so please verify it independently. Recipes may contain errors, so please use your common sense when following them. Please read our Terms of Use carefully before using any of our recipes.

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    About the Author

    Vered Deleeuw Vered DeLeeuw, LL.M., CNC, has been following a low-carb real-food diet and blogging about it since 2011. She's a Certified Nutrition Coach (NASM-CNC), has taken courses at the Harvard School of Public Health, and has earned a Nutrition and Healthy Living Certificate from Cornell University. Her work has appeared in several major media outlets, including Healthline, HuffPost, Today, Women's Health, Shape, and Country Living. Click to learn more about Vered.

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      Recipe Rating




    1. Holly

      September 13, 2023 at 1:15 pm

      5 stars
      You sure need patience, but wow, these onions are good. They are perfect with burgers and steaks!

      Reply
      • Vered DeLeeuw

        September 14, 2023 at 10:05 am

        I'm so glad you like this recipe, Holly!

        Reply
    2. Keri Bishop

      August 09, 2023 at 1:50 am

      5 stars
      Thank you so much for this detailed tutorial! It helped me be patient because I could visualize the stages of the onions getting caramelized. I used Vidalia onions and they turned out amazing! Almost like an onion jam.

      Reply
      • Vered DeLeeuw

        August 09, 2023 at 8:07 am

        You're most welcome, Keri!

        Reply

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    Healthy Recipes Blog was founded in 2011 by Vered DeLeeuw. It features real-food recipes with a focus on low-carb and gluten-free ingredients. All recipes are nutritionally reviewed by a Registered Dietitian. Contact us at HealthyRecipesBlog@gmail.com.


    👩🏻‍🍳 I aim to publish a new recipe once or twice a month. Want these recipes in your inbox? Subscribe today! You can unsubscribe at any time.

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