In a large pot, heat olive oil over medium heat. Add onion, carrots, and celery. Sauté for 5-7 minutes until softened and onion is translucent.

Add minced garlic, ground cumin, ground turmeric, salt, and black pepper. Stir and sauté for another minute until fragrant.

Stir in lentils and diced potatoes. Pour in water or vegetable broth and bring to a rolling boil.

Once boiling, reduce heat to low and let the soup simmer uncovered for 30-35 minutes, stirring occasionally.

Add spinach or Swiss chard during the last 5 minutes. Stir until wilted.

Remove from heat and stir in lemon juice. Adjust seasoning if needed.

Ladle warm soup into bowls, garnish with olive oil or lemon wedge if desired.