Rinse lentils thoroughly and set aside.
Heat olive oil in a large pot over medium heat.
Add chopped onions, garlic, and sauté until soft and fragrant.
Add chopped carrots and celery, and cook for a few minutes.
Add lentils, water or vegetable broth, and mix well.
Season with salt, black pepper, and spices like cumin or turmeric.
Bring to a boil, then simmer for 20–25 minutes until lentils are tender.
Adjust seasoning, garnish with fresh herbs, and serve hot.