In a large pot, heat the olive oil over medium heat.

Add the chopped onion, carrots, and celery to the pot. Sauté for about 5 minutes until the vegetables are softened and fragrant.

Stir in the minced garlic, cumin, and smoked paprika. Cook for about 1 minute until fragrant.

Add the lentils to the pot and stir to combine.

Pour in the vegetable broth and add the bay leaf. Bring to a boil.

Reduce to a simmer and let it cook for about 25 minutes or until the lentils are tender.

Stir in the chopped spinach or kale (if using) and cook for an additional 5 minutes.

Season the soup with salt and pepper to taste before serving.