Lentil Soup

A comforting, incredibly cheap, and nourishing soup that gets better the next day.

By Cressio Rinaldi

Lentil soup is the kind of recipe that proves cheap food can be deeply satisfying. A bag of lentils, a few vegetables and a pot of broth turn into something thick, earthy and filling enough to be dinner. It also gets better after a night in the fridge.

This version is built on a classic base of onion, carrot and celery, softened in olive oil, with garlic and cumin for warmth. Canned tomatoes add body and a little acidity. The lentils cook directly in the broth, so they release their starch and thicken the soup as they go.

The step people forget is the last one. A splash of lemon juice at the end wakes up the whole pot, and it is the difference between a soup that tastes fine and one that tastes bright.

Read this first

1. Rinse the lentils, and check for any small stones.
2. Simmer gently with the lid on, and check the lentils for tenderness at 35 minutes.
3. Finish with lemon juice and salt at the end, and taste before you serve.

Prep time: 10 mins · Cook time: 40 mins · Serves 6

Ingredients

• 1.5 cups Brown lentils, rinsed
• 2 tbsp Olive oil
• 2 Carrots, diced
• 2 stalks Celery, diced
• 1 Onion, diced
• 3 cloves Garlic, minced
• 1 tsp Ground cumin
• 6 cups Vegetable broth
• 1 can (14 oz) Diced tomatoes

Instructions

1. In a large pot, heat olive oil over medium heat. Sauté carrots, celery, and onion until soft, about 5 minutes. Look for: The onion is translucent, and the carrots and celery are softened and smell sweet.
2. Add garlic and cumin, cooking for 1 minute until fragrant. Look for: The garlic and cumin smell warm and fragrant, with no browning.
3. Add the rinsed lentils, vegetable broth, and diced tomatoes. Look for: The pot looks full of color, with lentils, tomatoes and vegetables in a bright broth.
4. Bring to a boil, then reduce heat, cover, and simmer for 35-40 minutes until lentils are very tender. Look for: A gentle simmer with the lid on, and lentils that are very soft when pressed.
5. Stir gently and season with salt, pepper, and a splash of lemon juice before serving. Look for: A thick, savory soup that tastes bright after the lemon.

Nutrition

Amount per serving. Nutritional values are estimates calculated from the ingredients above and can vary.

• Calories: 140
• Fat: 6g
• Saturated Fat: 1g
• Carbohydrates: 18g
• Fiber: 5g
• Sugar: 4g
• Protein: 6g
• Sodium: 880mg
• Cholesterol: 0mg

Notes

• Storage: Refrigerate in an airtight container for up to 5 days — the flavor deepens overnight.
• Freezing: Freezes well for up to 3 months; the lentils hold their texture nicely after thawing.
• Consistency: This soup thickens as it sits — thin leftovers with a splash of broth or water when reheating.

Cook It With Me

Soften the vegetables

Heat the 2 tablespoons of olive oil in a large pot over medium heat. Add the 2 diced carrots, 2 diced celery stalks and the diced onion. Cook them for about 5 minutes, stirring now and then, until they are soft and the onion is translucent.

Garlic and cumin

Add the 3 minced garlic cloves and the 1 teaspoon of ground cumin and cook for 1 minute, until the pot smells fragrant. Stir so the spices don’t stick.

Add the lentils and liquids

Add the 1 1/2 cups of rinsed brown lentils, the 6 cups of vegetable broth and the 14 oz can of diced tomatoes, with their juice.

Simmer

Bring the soup to a boil, then reduce the heat, cover and simmer for 35 to 40 minutes, until the lentils are very tender. Stir once or twice. If it gets too thick, add a splash of water.

Season and serve

Stir gently and season with salt, pepper and a splash of lemon juice. Taste it, and adjust. For a thicker soup, blend a cup of it with an immersion blender and stir it back in.

The Ingredients, One by One

Brown lentils

The most common lentil, cheap and available everywhere. They get very soft when cooked, which thickens the soup. Rinse them and check for small stones.

Carrots, celery and onion

The classic soup base. A similar dice makes them cook evenly. Softening them first builds flavor.

Garlic and cumin

Three cloves of garlic and one teaspoon of cumin give a warm, earthy flavor that fits lentils.

Vegetable broth

Six cups is the cooking liquid. A low-sodium broth lets you season the soup yourself.

Diced tomatoes

They add body, color and gentle acidity.

Lemon juice

A small splash at the end brightens everything.

The Technique Behind It

Why you soften the vegetables first

Cooking them in oil releases their sugars and builds a sweet base. Adding them raw to broth gives a thinner flavor.

Why you add the spices to the oil

Cumin’s flavor compounds dissolve in fat. A minute in the oil spreads the flavor through the soup.

Why lemon at the end

Acid brightens flavor, but its fresh taste fades with long cooking. Adding it at the end keeps it sharp and clear.

Mistakes That Cost You the Dish

• Not rinsing the lentils They can have dust or small stones.
• Boiling hard The lentils break down unevenly and can stick.
• Salting too early Broth and tomatoes are already salty.
• Skipping the lemon The soup tastes flat.
• Leaving the lid off The soup reduces too much.

Fix It: If This Happens, Do This

Problem	Likely cause	Fix
Soup is too thick	The lentils absorbed liquid	Stir in water or broth until it looks right.
Soup is too thin	Too much liquid	Simmer uncovered for 10 minutes, or blend part of the soup.
Soup is bland	Not enough salt or acid	Add salt, then lemon juice, a little at a time.
Lentils are hard	Old lentils or not cooked long enough	Keep simmering and add water if needed.
Soup stuck to the pot	The heat was too high	Lower the heat and stir often.

What Each Ingredient Does (and What You Can Swap)

Ingredient	Its job	Swap, and what changes
Brown lentils	Cheap, earthy and thickening	Green lentils hold their shape more. Red lentils cook faster and turn creamy.
Vegetable broth	Liquid and flavor	Chicken broth works.
Diced tomatoes	Body and acid	Crushed tomatoes give a smoother soup.
Cumin	Warmth and earthiness	Smoked paprika or curry powder work.
Olive oil	A base for the vegetables	Butter works.
Lemon juice	Brightness	Red wine vinegar works.

Plan Ahead

• Make ahead: The flavor improves overnight.
• Fridge: Up to 5 days in an airtight container.
• Reheat: On the stove with a splash of water.
• Freezer: Freezes well for up to 3 months.

What to Serve With It

Serve with crusty bread, a drizzle of olive oil and a little parmesan, if you like. A dollop of yogurt and fresh parsley or cilantro on top is also good.

Questions People Ask

About the Author

Cressio Rinaldi

Cressio Rinaldi is the recipe developer behind Cressio Recipes. He cooks, tests, and writes every recipe on the site himself — refining each one until it's simple enough for a weeknight and good enough to make again. He's not a trained chef, just someone who cooks constantly and pays close attention to what actually makes a recipe work.