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Low-Carb Roast Onion Soup

Dearna BondUpdated 20 November 2023★★★★★4.7 (68 ratings)
  • Ready in 1h
  • 7.1 g net carbs
  • 269 kcal
  • Serves 6
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Low-Carb Roast Onion Soup (keto, vegetarian, grain-free)

This keto riff on French onion soup uses cauliflower to lower the carb content. By roasting the cauliflower and onion together, the onions flavour is intensified and the resulting soup is rich and flavoursome.

You can substitute the fresh onion and cauliflower here for frozen cauliflower and onion, or alternatively if you want to freeze the soup, you can double or triple the quantities and portion out to freeze.

This low-carb soup is delicious served with some grated Swiss cheese melted on top, or even with a piece of toasted keto bread.

Step-by-step

  1. Heat oven to 190 °C/ 375 °F (conventional), or 170 °C/ 340 °F (fan assisted). Chop the cauliflower into florets and slice the onion.

    Low-Carb Roast Onion Soup (keto, vegetarian, grain-free)

  2. Place in a roasting dish and toss with the garlic cloves, olive oil, salt and pepper.

  3. Bake for about 45 minutes, stirring half way through, until the vegetables are nicely browned but not burnt.

    Low-Carb Roast Onion Soup (keto, vegetarian, grain-free)

  4. Remove from the oven and add the cauliflower and onion to a pot with the stock and water.

  5. Squeeze the garlic from the skins into the pot. Bring to a simmer and cook for about 10 minutes.

    Low-Carb Roast Onion Soup (keto, vegetarian, grain-free)

  6. Remove from heat and serve topped with grated cheese. Store in the fridge up to 5 days or freeze for up to 3 months.

    Low-Carb Roast Onion Soup (keto, vegetarian, grain-free)
Low-Carb Roast Onion Soup

Recipe

Low-Carb Roast Onion Soup

★★★★★4.7 (68 ratings)

This easy low-carb French onion soup is made with sweet onions and cauliflower roasted until caramelized and ...

Hands on
10m
Overall
1h
Servings
6
7.1 g
Net carbs
8.5 g
Protein
22.5 g
Fat
269
kcal
PinRate

Ingredients makes 6 servings

Instructions

  1. Heat oven to 190 °C/ 375 °F (conventional), or 170 °C/ 340 °F (fan assisted). Chop the cauliflower into florets and slice the onion.

  2. Place in a roasting dish and toss with the garlic cloves, olive oil, salt and pepper.

  3. Bake for about 45 minutes, stirring half way through, until the vegetables are nicely browned but not burnt.

  4. Remove from the oven and add the cauliflower and onion to a pot with the stock and water.

  5. Squeeze the garlic from the skins into the pot. Bring to a simmer and cook for about 10 minutes.

  6. Remove from heat and serve topped with grated cheese. Store in the fridge up to 5 days or freeze for up to 3 months.

Nutrition per serving, about 1 ⅓ cups/ 320 ml

Carbs 11%Protein 13%Fat 76% of calories

Net carbs
7.1 g
Total carbs
9.9 g
Fiber
2.8 g
Sugars
4.7 g
Protein
8.5 g
Fat
22.5 g
Saturated fat
9.4 g
Calories
269 kcal
Sodium
498 mg · 21.7% RDA
Magnesium
35 mg · 8.82% RDA
Potassium
560 mg · 28% EMR
Nutrition by ingredient
Per about 1 1/3 cups/ 320 mlNet carbsProteinFatkcal
Onion, brown (yellow), raw3.2 g0.5 g0 g18
Cauliflower, fresh2.2 g1.4 g0.2 g19
Garlic, fresh0.6 g0.1 g0 g3
Olive oil, extra virgin0 g0 g9 g80
Salt, sea salt0 g0 g0 g0
Pepper, black, spices0 g0 g0 g0
Vegetable stock1 g0.8 g7.2 g72
Water, still0 g0 g0 g0
Cheese, Swiss , Gruyère0.1 g5.6 g6 g78
Total7.1 g8.5 g22.5 g269

Serving size about 1 1/3 cups/ 320 ml

  • Gluten free
  • Egg free
  • Nut free
  • Nightshade free
  • Pork free
  • Avocado free
  • Coconut free
  • Fish free
  • Shellfish free
  • Beef free
  • Pescatarian
  • Vegetarian

Goes well with

Add a side and it's a complete meal.

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Comments & ratings (7)

4.768 ratings
  • 5 ★58
  • 4 ★5
  • 3 ★2
  • 2 ★0
  • 1 ★3

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  1. Judy M

    This is excellent! And so easy!
    I was surprised how easy it came together. It’s pretty much roasting the vegetables.
    But it’s not a straightforward as I thought. When you give 10.6 ounces For the onion, are you meaning 10.6 ounces each? Or 10.6 ounces total? Because my large onion was 10.6 ounces. Since I didn’t know what you meant, I did one and a half just to be sure.
    Same thing with the cauliflower.
    Just glad it’s cooking and not baking, where you have to be precise
    I would love it if you clarified the measurements.
    I couldn’t figure out where to write it. Five stars! I kept clicking on the stars and it took me to the top of the page.
    Thank you for your hard work! Judy and Larry.

    1. Martina @ KetoDietAuthor

      Hi Judy, thank you so much for the lovely feedback! All weights are per totals so the 10.6 oz is weight per 2 large onions but I know what you mean as "large" can be subjective. I hope this helps!

  2. Judy M

    This looks so good, and I’d like to make it. How would it be if I left the cheese out?

    1. Martina @ KetoDietAuthor

      His Judy, I'd say quite plain as the cheese is one of the key ingredients.

      1. Judy M

        Thanks! I added some vegan smoked Gouda by follow your heart, after seeing your comments

  3. Juli Hutson

    THIS WAS A BIG HIT!!♥️♥️
    Smelled so delicious in my house, I used my immersion blender so my husband could eat without his teeth in! He and my daughter and of course myself loved it! I will be making this soup again!! Thank you for sharing

    1. Martina @ KetoDietAuthor

      Glad you enjoyed Juli! ❤️

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