Rinse lentils under cold water and set aside. Prepare celery, carrots, onions, and garlic according to the specified quantities.
In a large pot, heat olive oil over medium heat. Add chopped onions, minced garlic, celery, and carrots. Sauté until the vegetables are softened and the onions are translucent.
Introduce the rinsed lentils to the pot, stirring them into the aromatic mix. Add chopped cilantro and continue stirring to combine the flavors.
Pour in the chicken broth, ensuring it covers the lentils and vegetables. Bring the mixture to a gentle boil. Reduce the heat to low, cover the pot, and let the soup simmer for approximately 30-40 minutes or until the lentils are tender. Stir occasionally to prevent sticking.
Season the soup with salt and pepper to your liking. Stir well, allowing the flavors to meld for an additional 5-10 minutes.
Ladle the hot lentil soup into bowls. Garnish with additional cilantro if desired.
Notes: Adjust the consistency by adding more broth if needed.