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Keto French Onion Soup

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4.91 from 272 votes
By Carine - - 6 Comments

Keto French Onion Soup is a low-carb version of the traditional classic French onion soup recipe. Sweet caramelized onion simmered into a beef broth with cheesy keto bread croutons topped with French swiss cheese.

Low-carb French onion soup

Can I have French onion soup on keto?

No, you can’t! Traditional French onion soup has many high-carb ingredients. But wait! I have created a 100% keto-friendly French onion soup!

Keto French onion soup

As a French girl on a keto diet, I love French onion soup, so I had to recreate a keto version of my family’s traditional French onion soup recipe!

Is French onion soup keto?

If you wonder, is French onion soup keto-friendly? Well, no! A traditional French onion soup is not keto-approved. Below I listed all the ingredients and reasons why you shouldn’t eat a traditional French onion soup on keto:

  • Sugar. a classic French onion soup requires onions that are caramelized in sugar. Sugar is your worst enemy on keto since it is pure carbs. Only 10 grams is 10 grams of net carbs!
  • White wheat flour. this is used to help thicken the soup, and like sugar, flour is pure carbs, so not for you on keto!
  • White wine. White wine is used to deglaze the onions. You can have some dry white wine on keto if used in moderation, but unfortunately, the classic French onion soup uses quite a good amount, which brings the carbs very high.
  • Croutons. A classic French onion soup is always topped with lots of toasted French bread. Again, regular bread is not keto-friendly as it is made with wheat flour, high in carbs.

So, as you can see, you can’t eat a classic onion soup recipe. But let me show you how French onion soup and keto can work together!

How to make keto French onion soup?

There are a few necessary tweaks to make an onion soup keto-friendly. Let me show you how to select the ingredients to make a keto low-carb French onion soup.

Soup ingredients

  • White onion. Onions are naturally high in carbs, so I use fewer onions in my keto version of the French onion soup. Still, a good enough amount to bring texture and flavor. Don’t use red onions. They are higher in carbs, and the soup would be very sweet.
  • Erythritol. It’s the swap to sugar, and it is a 100% keto-friendly keto sweetener that can caramelize onion just as well without adding any carbs.
  • Beef bone broth. Also known as keto beef stock sometimes, it’s 100% keto-friendly, so you are safe here. If you want to make a vegetarian French onion soup, swap beef bone broth for vegetable broth.
  • Xanthan gum. This is your thickening agent. It contains barely any carbs and replaces high-carb flour found in the traditional French recipe.
  • White wine. Not all white wines are keto-friendly. You must use dry white wine like Sauvignon blanc. I also reduced the amount in this recipe to keep the net carbs per serving under control while having the tangy wine flavor.
  • Bay leaves. The secret French herb to any good French onion soup and many French dishes.
  • Thyme
  • Salt. Optional if your beef broth is already high in salt.

Preparing the soup broth

It is super easy to make an onion soup. First, heat the butter, add finely sliced white onion, and cook for 20-25 minutes until soft, brown, and fragrant.

Then, add erythritol and salt to caramelize the onion. Finally, deglaze the onions with dry white wine and beef broth.

French onion soup

How to make onion soup toppings keto?

The best part of French onion soup is these crunchy croutons and broiled bubbly cheese on top! You don’t want to miss this even on keto so let me share my tricks to making quick keto croutons to add on top of your soup.

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A traditional French onion soup is not topped with small bread croutons but with a thin French baguette slice.

is French onion soup keto

As a French person, let me share the secret for this!

French people eat baguettes daily, and the slice of baguette on top of the onion soup is most of the time a stale baguette that has hardened on the kitchen countertop.

Then, we slice thin pieces of hard baguette and toast it in a bread toaster or oven to get it very hard and crispy.

Carine from Sweetashoney

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By Carine from Sweetashoney

Finally, we spread fresh butter on the bread and rub a fresh garlic glove to flavor it.

This is then added on top of the onion soup and French grated cheese: usually Emmental, gruyere, or swiss cheese, and broil in the oven.

Keto crouton recipe

Of course, you can’t eat regular French bread or croutons on a keto diet. But I have a few solutions for you to mimic crispy croutons into your soup.

Make a quick keto microwave bread

My favorite option is to make my 90-second keto microwave bread recipe in a tall cylinder coffee mug. This keto recipe mimics the baguette shape.

Then, release the bread cylinder and slice into thin bread slices. The slices will be very soft so bring them into a bread toaster on high until crispy.

Keto croutons

Then, spread butter on the toasted bread slices and rub fresh garlic on the bread – onions and garlic are delicious, don’t skip! 

French onion soup keto

Finally, top your keto onion soup bowl with a slice of this keto crouton recipe, add cheese and broil!

Et voila! You made a keto French onion soup. If someone asks you if you can eat French onion soup on a keto diet, you can proudly answer YES, and serve this yummy recipe!  

Using store-bought crouton alternatives

If you don’t feel like baking, use some of the options below to mimic croutons into your keto soup:

  • Pork rinds: that’s the closest alternative to croutons, and it contains zero carbs, so it’s a great addition to your keto meal.  
  • Toasted seeds: like sunflower or pumpkin seeds.
  • Parmesan crisp

How to store onion soup?

Onion soup stores very well in the fridge for up to 5 days in a sealed container.

You can rewarm the soup in a saucepan or microwave. Then, broil in the oven with shredded cheese.

French onion soup and keto

How much can I eat?

This recipe serves 8 bowls. Serving size is 1 cup of soup and 1 slice of keto crouton and cheese. The entire low-carb onion soup bowl, including bread slices, contains 7.8 grams of net carbs or 6.1 grams of net carbs without the keto bread.

can I have French onion soup on keto

More keto soup recipes

Below I listed more keto soup recipes for you to try:

Enjoy the lovely Keto French recipe, and don’t forget to leave me a comment below if you made it and review it!

You can also follow me on Pinterest for more keto inspiration.

XOXO Carine

Recipe Card

Keto French Onion Soup

Low carb French onion soup
6.1gNet Carbs
4.91 from 272 votes
Prep Time: 30 mins
Total Time: 30 mins
Net Carbs 6.1g
Fat 14.2g
Protein 10.3g
Calories 202.7kcal
Author: Carine Claudepierre
8 people (1 cup = 1 serving)
A keto low-carb version of the popular French onion soup.

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Net Carbs
4.91 from 272 votes
Leave A Review Print The Recipe


  • 3 tablespoons Butter
  • 1 ¼ pounds Onions thinly sliced (about 3 large onions)
  • 1 tablespoon Erythritol
  • ¼ teaspoon Salt
  • ¼ teaspoon Xanthan Gum
  • 6 cups Beef Broth
  • cup Dry White Wine like sauvignon blanc or replace by more beef broth if preferred
  • ½ teaspoon Dried Thyme
  • 2 Bay Leaves

For the keto bread toast

  • 1 batch Keto 90-seconds Microwave Bread cook in a tall cylinder coffee mug
  • 1 tablespoon Butter
  • 1 Garlic Clove
  • 1 ½ cup French Gruyere Cheese grated
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  • In a large pot, heat butter and onions over medium heat.
  • Cook onion until they soften- about 2 minutes, then add salt and erythritol.
  • Reduce to medium/low heat and continue cooking/stirring the onion until they become fragrant and golden brown. This takes about 20-25 minutes. Make sure you stir often to avoid burning the onion.
  • Sprinkle the xanthan gum all over the cooked onion, add beef stock, low-carb white wine if used (or more beef broth if preferred), dried thyme, and bay leaves. Cover and simmer for 30 minutes.

Keto bread crouton

  • Meanwhile, prepare the keto croutons. Make 1 batch of my 90-second keto microwave bread recipe. Make sure you bake the recipe into a tall cylinder shape coffee mug (microwave safe!)
  • Cook your keto bread in the microwave following the recipe here. Release the bread cylinder from the mug, cool for 1 minute to steam out (this also avoids burning yourself), then cut into 4 even slices. You can repeat this bread recipe to make 4 more croutons if you intend to serve 8 soup bowls.
  • Bring each bread slice into a bread toaster on high and toast until crispy on both sides. Set aside on a plate to cool.
  • Preheat oven to 350°F (180°C). When the oven is hot, turn to broil mode.
  • Remove bay leaves from the soup and discard.

Serve the soup

  • Ladle soup into 8 oven-proof soup bowls – 1 cup is 1 serving.
  • Brush some butter on top of each slice of toasted keto bread. Rub a fresh garlic glove on the bread slices to flavor the bread.
  • Place 1 toasted bread slice on top of each bowl.
  • Cover the top of each soup bowl with 1/3 cup of grated French gruyere.
  • Broil in the oven until the cheese is brown.
  • Serve immediately.


  • Store leftover soup in an airtight sealed container in the fridge for 3-4 days.
The net carbs in the nutrition panel below don’t include the slice of 90-second bread recipe on top of the soup. Add 1.6 grams of net carbs per slice, if bread is cut into 4 slices or 1 gram if you cut the bread into 6 slices. Follow my bread recipe here and bake it in a tall coffee mug to create keto croutons that looks like French baguette slices.
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Nutrition Facts
Keto French Onion Soup
Amount Per Serving (1 soup (1 cup))
Calories 202.7 Calories from Fat 128
% Daily Value*
Fat 14.2g22%
Saturated Fat 8.5g53%
Cholesterol 42.3mg14%
Sodium 881.6mg38%
Potassium 227.8mg7%
Carbohydrates 7.4g2%
Fiber 1.3g5%
Sugar 3.2g4%
Protein 10.3g21%
Vitamin A 409.6IU8%
Vitamin C 5.4mg7%
Calcium 278.6mg28%
Iron 0.6mg3%
Net Carbs 6.1g
* Percent Daily Values are based on a 2000 calorie diet.
Low carb French onion soup

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    6 thoughts on Keto French Onion Soup
  1. 5 stars
    Made it tonight and it was spot on perfect comfort food! Simple ingredients and very easy to make. I omitted the croutons to save carbs, but might melt cheese on it tomorrow. Thanks for sharing this. I will be trying out more of your recipes soon!

  2. Hi Carine, I am planning on making this recipe tonight! Unfortunately, I don’t have any xanthan gum saved. Do you have any low carb recommendations I could use as a substitute? Otherwise, I could try and go buy some if it is absolutely needed.

    Look forward to hearing from you!

  3. There are way too many ingredients in your soup. My absolute favourite French Onion Soup is in the NZ Edmonds Cook Book. It does have sugar, but I don’t put any in my soup. Nor do I put in the sherry. I don’t eat red meat, so leave out the beef stock and put in vegetable. Whenever onions are in season I put in the 5 ingredients of butter, onion, stock, salt & pepper and happily have soup for many nights.

    • I am not sure what you mean, this soup contains 9 ingredients, including 5 that are herbs or flavoring. You can obviously these 5 herbs but your soup will lack in flavor. Here my goal is to share an adaptation of the classic French soup recipe I used to eat as a kid (I am French). I am sorry you don’t appreciate it. Enjoy the blog, XOXO Carine


The recipes, instructions, and articles on this website should not be taken or used as medical advice. You must consult with your doctor before starting on a keto or low-carb diet. The nutritional data provided on Sweetashoney is to be used as indicative only. The nutrition data is calculated using WP Recipe Maker. Net Carbs is calculated by removing the fiber and some sugar alcohols from the total Carbohydrates. As an example, a recipe with 10 grams of Carbs per 100 grams that contains 3 grams of erythritol and 5 grams of fiber will have a net carbs content of 2 grams. Some sugar alcohols are excluded because they are not metabolized. You should always calculate the nutritional data yourself instead of relying on Sweetashoney's data. Sweetashoney and its recipes and articles are not intended to cure, prevent, diagnose, or treat any disease. Sweetashoney cannot be liable for adverse reactions or any other outcome resulting from the use of recipes or advice found on the Website.

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