Lusciously Lemony Lentil Soup

⏲ ~52 min total · prep 17 · cook 35 · 4 servings

By the KFI Test Kitchen · Tested & approved by Jason Lieu, KFI recipe editor

Published Sep 15, 2026 · Updated Sep 15, 2026

Ingredients

• 1/3 cup dry green or brown lentils, rinsed
• 1 small head cauliflower, cut in 1/2-inch florets
• 3 tbsp olive oil
• 1 medium yellow onion, diced
• 1 medium carrot, diced small
• 3 cloves garlic, minced
• 1 tsp ground cumin and 1/2 tsp ground coriander
• 1 bay leaf
• 5 cups chicken or vegetable broth
• 1 tbsp lemon zest
• 1/4 cup fresh lemon juice (about 2 lemons)
• 2 tbsp chopped fresh dill

Instructions

1. Heat the olive oil in a 4-quart pot over medium and cook the onion and carrot 8 minutes, stirring now and then, until translucent and sweet-smelling with no browning.
2. Add the garlic, cumin, and coriander and stir 45 seconds, just until fragrant.
3. Pour in the broth, add the lentils, cauliflower, and bay leaf, and bring to a boil, then set the lid ajar and simmer gently 25 minutes, until the lentils are creamy-tender and the cauliflower is collapsing; top with a splash of water if it thickens past a loose soup.
4. Ladle 1 cup of the soup into a blender, blend smooth, and stir it back into the pot for body while plenty of lentils and florets stay whole.
5. Fish out the bay leaf and take the pot off the heat before adding the lemon zest and juice — heat drives off their brightness.
6. Taste; it should spark with lemon, so add more juice by the teaspoon if it does not.
7. Ladle into bowls and finish each with dill, a grinding of pepper, and a thin thread of olive oil.

Why this recipe works

• Where the 24 carbs live At 24.0 net carbs a serving, this is a budget-spending bowl, and the lentils spend most of it. A whole head of cauliflower fills out the volume, so a third of a cup of dry lentils still reads generous.
• Blend one cup only Blending a single ladleful and stirring it back gives the pot body while most of the florets and lentils stay whole. Puree everything and you lose the contrast that makes the texture interesting.
• Lemon off the heat Zest and juice go in after the burner goes off. Heat drives off the brightness that makes this soup what it is, which the method respects.

Tips for making this recipe well

No browning on the onions

Eight minutes over medium should leave them translucent and sweet-smelling. Browned edges change the soup's character and fight the lemon. Stir now and then and keep the heat honest.

Keep it loose

Lentils keep drinking broth as the pot sits, on the stove and in the fridge. The recipe calls for a loose soup, so add a splash of water whenever it passes that line. Day two almost always needs it.

Zest before you juice

Zesting two lemons is easy whole and miserable once they are halved and squeezed. Take the zest first, then juice them for the quarter cup. A microplane over the pot catches every strand.

Taste for the spark

The recipe says the finished soup should spark with lemon, and that test is the point. Add juice by the teaspoon until it does. Under-lemoned, this tastes like a different and worse soup.

Dill on each bowl

Chopped dill goes on each serving, not into the pot, so it stays green and tastes like dill. A grinding of pepper and a thin thread of olive oil finish it. Do this at the table, not the stove.

Serving suggestions

Ladle into wide bowls and finish each with dill, black pepper, and a thread of olive oil, exactly as the method ends it. At 24.0 net carbs this is a deliberate bowl rather than an everyday keto one, so plan the rest of the day around it. A wedge of the zested lemons on the side lets each eater push the lemon further. Bread is the usual partner and stays off the table here; the cauliflower does the body work instead.

Storage and meal prep

The pot keeps 3 to 4 days refrigerated, and the lentils thicken overnight, so loosen each reheated portion with a splash of water or broth. Warm it gently rather than boiling. The first dose of lemon dulls in storage, so finish each reheated bowl with a fresh squeeze. Freezing for 2 to 3 months works, though the cauliflower turns softer than a fresh batch. Taste and rebalance the lemon before it goes back on the table.

Variations worth trying

• Red lentils Red lentils cook faster and dissolve, which turns the pot thick and uniform. Skip the blending step and check early for doneness.
• Vegetarian broth Vegetable broth in place of chicken makes the pot meatless with no other changes. The cumin and coriander carry it.
• Extra cauliflower A second head of cauliflower, cut the same half-inch size, stretches the pot at little carb cost. Simmer it in the same 25 minutes.
• Chile oil finish Soften a pinch of red pepper flakes in the finishing olive oil and drizzle it over each bowl. The lemon and dill keep the warmth in check.

Frequently asked questions

Is lentil soup keto?

At 24.0 net carbs a serving it is not an everyday keto bowl, and we would rather print the number than hide it. The lentils carry most of that count. Treat it as a planned meal if you track carbs closely.

Can I skip the blender step?

You can, and the soup will be thinner and more broth-forward. Blending one cup takes a minute and gives the pot its body. An immersion blender works if you dislike transferring hot soup.

Which lentils work best?

The recipe calls for green or brown lentils, rinsed, and both hold their shape through the 25-minute simmer. Red lentils fall apart and change the character of the pot. Older lentils also take longer to soften.

Why did my soup get so thick?

Lentils absorb broth as they rest, both on the stove and in the fridge. The recipe anticipates this and says to loosen with a splash of water past a loose-soup texture. Do the same when reheating.

Can I add the lemon earlier?

You can stir it in early, but heat drives off the brightness the zest and juice bring. The method adds them off the heat for that reason. If you prep ahead, add the lemon when you reheat.

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