In a large pot, heat olive oil over medium heat. Add the diced onion, garlic, and sauté until the onion becomes translucent, about 5 minutes.
Stir in the diced carrot and celery, cooking for an additional 4-5 minutes until slightly softened.
Sprinkle the turmeric and cumin over the sautéed vegetables, stirring well to coat everything. Cook for another minute until fragrant.
Add the rinsed lentils and vegetable broth to the pot. Bring to a boil, then reduce heat to a simmer. Cover and let it cook for about 25-30 minutes, or until the lentils are tender.
Once the lentils are cooked, stir in the lemon zest and juice, and season with salt and pepper to taste.
For a creamier texture, use an immersion blender to blend a portion of the soup (optional).
Serve hot, garnished with fresh cilantro or parsley.
Notes
For a creamier texture, use an immersion blender to blend a portion of the soup.