Heat olive oil in a large pot over medium heat.
Sauté onion, garlic, celery, and carrots until softened (about 5–7 minutes).
Add cumin and turmeric; stir for 1 minute until fragrant.
Pour in green lentils and vegetable broth. Bring to a boil.
Reduce heat and simmer for 25–30 minutes, until lentils are tender.
Stir in chopped spinach/kale and cook for another 5 minutes.
Season with salt, pepper, and lemon juice.
Garnish with fresh parsley and serve hot.