Heat olive oil in a large pot over medium heat. Add diced onion, garlic, carrots, and celery. Sauté for about 5 minutes until softened.

Stir in turmeric, cumin, black pepper, and salt. Cook for another minute until fragrant.

Add the rinsed lentils and vegetable broth to the pot. Bring to a boil, then reduce heat to low and simmer for 25-30 minutes, or until lentils are tender.

Stir in the spinach and cook for an additional 5 minutes until wilted. Adjust seasoning if necessary.

For a creamier texture, blend a portion of the soup and return it to the pot.