In a large pot, heat the olive oil over medium heat. Add the diced onion, carrots, and celery. Sauté for about 5-7 minutes until the vegetables are softened.
Stir in the minced garlic, cumin, smoked paprika, and oregano. Cook for another minute until fragrant.
Add the rinsed lentils, vegetable broth, and diced tomatoes along with their juices to the pot. Bring to a boil.
Reduce the heat to low and let the soup simmer gently for about 25-30 minutes, or until the lentils are tender.
In the last 10 minutes of simmering, add the diced zucchini and spinach (or kale). Stir well and simmer until just tender.
Once cooked, stir in the lemon juice and season the soup with salt and pepper to taste.
Serve hot, garnished with fresh parsley.
Notes
Feel free to add other vegetables or spices to your liking.