This light lentil soup is a brothy, vegetable-filled meal made with brown or green lentils, carrots, celery, tomatoes, and a bright squeeze of lemon. It comes together in one pot without cream, and the lentils make it satisfying while keeping the broth clean and simple.
Ingredients
- 1 tablespoon extra-virgin olive oil (15 ml)
- 1 medium yellow onion, diced (about 150 g)
- 2 medium carrots, diced (about 150 g)
- 2 celery ribs, diced (about 100 g)
- 3 garlic cloves, minced (about 9 g)
- 1 teaspoon ground cumin (2 g)
- ½ teaspoon dried thyme (about 0.5 g)
- 1 cup dried brown or green lentils, rinsed and picked over (190 g)
- 1 can (14.5 ounces/411 g) diced tomatoes, with their juices
- 6 cups low-sodium vegetable broth (1.4 L), plus more as needed
- 1 bay leaf
- ¾ teaspoon fine salt, plus more to taste (about 4.5 g)
- ¼ teaspoon freshly ground black pepper (about 0.5 g)
- 2 cups chopped baby spinach or chopped kale, loosely packed (about 60 g spinach or 70 g kale)
- 2 tablespoons fresh lemon juice (30 ml), plus lemon wedges to serve
- 2 tablespoons chopped fresh parsley (about 8 g), optional
Instructions
- Prepare the lentils. Rinse them in a fine-mesh strainer under cool running water, removing any shriveled lentils or small debris. Brown or green lentils are a good choice because they hold their shape better than red lentils during simmering.
- Soften the vegetables. Warm the olive oil in a large, heavy-bottomed pot over medium heat. Add the onion, carrots, and celery, and cook for 6 to 8 minutes, stirring occasionally, until softened but not browned. If the vegetables begin to stick, add a tablespoon of water rather than extra oil.
- Add aromatics and lentils. Stir in the garlic, cumin, and thyme; cook for about 30 seconds, just until fragrant. Add the rinsed lentils, diced tomatoes and their juices, broth, bay leaf, salt, and pepper. Stir and scrape the bottom of the pot so no garlic or spices are stuck there.
- Simmer until tender. Bring the soup to a boil, then reduce the heat to maintain a gentle simmer. Partially cover the pot and cook for 25 to 30 minutes, stirring once or twice, until the lentils are tender but not falling apart. The exact time varies with the lentils’ age and size. Add a little hot water or broth if the soup becomes thicker than you like.
- Finish the soup. Remove and discard the bay leaf. Stir in the spinach and cook for 1 to 2 minutes, just until wilted; if using kale, simmer for 3 to 5 minutes, until tender. Turn off the heat, stir in the lemon juice, and taste. Add salt, pepper, or more lemon as needed. Stir in parsley if using and serve hot.
Tips
- Check lentils before cooking. Older lentils can take longer to soften. If they are still firm after 30 minutes, continue simmering and check every 5 minutes; acidic tomatoes can slow softening, so do not add extra lemon until the end.
- Keep the simmer gentle. A hard boil can split the lentils and make the vegetables mushy. A slow bubble cooks them more evenly while preserving their shape.
- Adjust thickness at the end. Lentils keep absorbing liquid as they sit. Add hot broth or water for a looser soup, or simmer uncovered briefly if you prefer it thicker.
- Choose the right lentils. Brown and green lentils give a light, brothy texture. Red lentils break down more quickly, so if substituting them, start checking after 15 minutes and expect a thicker, softer soup.
Serving Suggestions
Serve the soup in warm bowls with lemon wedges so everyone can brighten their portion to taste. A slice of whole-grain bread, toasted pita, or a simple green salad makes an easy accompaniment. For a more substantial meal, add a spoonful of plain yogurt or a small sprinkle of crumbled feta; these are optional toppings rather than ingredients needed for the base recipe.
Variations
For a little heat, add ¼ teaspoon red pepper flakes with the garlic and spices. To make the soup more herb-forward, stir in chopped dill or cilantro along with the parsley. You can replace the spinach with chopped Swiss chard, adding its stems with the carrots and leaves near the end, or use kale as directed. For a deeper savory flavor, replace up to 2 cups (480 ml) of the broth with water and add a teaspoon of tomato paste with the garlic; the soup will taste slightly richer without becoming creamy.
For a fully plant-based version, check that the broth is vegetable broth and finish with olive oil rather than dairy toppings. If you prefer a smoother bowl, blend one or two cups of the cooked soup and stir it back into the pot; avoid blending the whole batch if you want the lentils and vegetables to remain distinct.
Storage and Reheating
Cool leftovers promptly and refrigerate them within 2 hours of cooking in shallow, covered containers. The soup keeps for 3 to 4 days in the refrigerator. It thickens as it chills, so loosen portions with water or broth when reheating. Warm on the stovetop over medium-low heat, stirring occasionally, or microwave in a covered, microwave-safe bowl, stirring partway through. Reheat leftovers to 165°F (74°C); check with a food thermometer if uncertain.
For longer storage, freeze cooled soup in airtight, freezer-safe containers for up to 3 months, leaving a little room for expansion. Thaw overnight in the refrigerator or reheat from frozen over low heat, stirring as it loosens. Add fresh lemon juice after reheating if the flavor needs refreshing.
Frequently Asked Questions
Do I need to soak lentils first?
No. Brown and green lentils cook directly in the soup after rinsing. Soaking is unnecessary and would change the timing, though you can soak them separately if you want to shorten their simmer; drain them and begin checking for tenderness earlier.
Can I use canned lentils?
Yes. Drain and rinse about 3 cups (720 ml) of canned lentils, then add them after the tomatoes and broth have simmered for about 15 minutes. Simmer another 5 to 10 minutes to heat them through and let the flavors combine; use less salt until you taste the finished soup.
Why are my lentils still firm?
They may be old, or the soup may not have simmered long enough. Continue cooking gently and add broth or water if needed. Tomato acidity can also slow tenderizing, so avoid adding extra acidic ingredients until the lentils are soft.
Can I make this soup in advance?
Yes. The flavor holds well, but the lentils absorb broth as the soup rests. Store it refrigerated within 2 hours and add broth or water when reheating. For the freshest citrus flavor, stir in a little extra lemon just before serving.
Is this soup gluten-free?
The listed ingredients are naturally gluten-free, but check the label on your vegetable broth and any packaged toppings if gluten is a concern. Serve with gluten-free bread or rice instead of wheat bread.
Can I make it without tomatoes?
Yes. Leave out the canned tomatoes and use an additional 1½ cups (360 ml) broth or water. The result will be milder and less tangy, so taste at the end and add lemon gradually to balance it.
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