Keto French Onion Soup
All the deep, caramelized comfort of classic French onion soup made keto-friendly at just 7.5g net carbs per serving. Slow-cooked onions in rich beef broth, topped with a bubbling Gruyere crust over a toasted almond-flour crouton. Ready in about 1 hour 5 minutes.
Head of Nutrition · June 17, 2026
Nutrition per serving
Per serving · makes 4. Values are estimates; brands vary.
This keto French onion soup delivers all the cozy, caramelized depth of the bistro classic without the carb-heavy baguette. Slow-cooked onions, rich beef bone broth, and a blistered Gruyere crust make it a soul-warming low-carb dinner.
Ingredients
- 3 tablespoons unsalted butter
- 1 tablespoon extra-virgin olive oil
- 2 medium yellow onions (about 12 oz total), thinly sliced
- 2 cloves garlic, minced
- 1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried)
- 1/4 cup dry red wine (optional, for deglazing)
- 5 cups beef bone broth (low-sodium)
- 1 tablespoon Worcestershire sauce
- 1 bay leaf
- Salt and black pepper, to taste
- 4 oz Gruyere cheese, shredded (about 1 cup)
- 4 keto almond-flour crackers or 4 slices keto bread, toasted (optional, for topping)
Instructions
- 1
Melt the butter with the olive oil in a heavy-bottomed pot or Dutch oven over medium-low heat. Add the sliced onions and a pinch of salt, stirring to coat.
- 2
Cook the onions low and slow for 30-35 minutes, stirring every few minutes, until deeply golden brown and jammy. Lower the heat if they start to scorch — patient caramelization is what builds the flavor.
- 3
Add the garlic and thyme and cook 1 minute until fragrant. Pour in the red wine (if using) and scrape up the browned bits from the bottom of the pot, simmering until nearly evaporated.
- 4
Add the beef bone broth, Worcestershire sauce, and bay leaf. Bring to a simmer and cook uncovered for 15 minutes. Remove the bay leaf and season with salt and pepper to taste.
- 5
Heat the broiler. Ladle the soup into 4 oven-safe bowls, top each with a toasted keto crouton (if using), and pile the shredded Gruyere over the top.
- 6
Broil 2-4 minutes until the cheese is melted, bubbling, and golden. Serve immediately, watching for hot bowls.
Tips & notes
- The single most important step is caramelizing the onions slowly — rushing on high heat burns them and turns the soup bitter. Keep the heat low and stir often.
- Skip the crouton entirely to drop the net carbs further, or use a low-carb cheese crisp as the base. The cheese alone melts beautifully right on the soup.
- Store leftover soup (without the cheese topping) in the fridge up to 4 days. Reheat, add fresh cheese, and broil just before serving.
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Frequently asked questions
- How many carbs are in keto french onion soup?
- Each serving has 7.5g net carbs (9.5g total carbs minus 2g fiber), 342 calories, 16g protein, and 26g fat. This recipe makes 4 servings, with most of the carbs coming from the caramelized onions.
- Why is regular French onion soup not keto?
- Traditional versions use a thick slice of crusty baguette and sometimes flour to thicken the broth, both high in carbs. This keto version swaps the baguette for a toasted almond-flour crouton (or skips it) and relies on slow-caramelized onions and rich bone broth for body.
- Can I make this dairy-free?
- Yes — use olive oil or a vegan butter in place of butter, and top with a dairy-free melting cheese. The flavor base comes from the caramelized onions and beef broth, so it still tastes rich without the Gruyere.
