Prepare the Base:
Heat the olive oil in a large pot over medium heat. Add the onion, carrots, and celery, and sauté for 5–7 minutes until softened.
Add Garlic and Spices:
Stir in the garlic, cumin, smoked paprika, and thyme. Cook for 1–2 minutes until fragrant.
Add Lentils and Liquid:
Add the lentils, diced tomatoes (with their juice), vegetable broth, and bay leaf. Stir well to combine.
Simmer:
Bring the soup to a boil, then reduce the heat to low. Cover and simmer for 25–30 minutes, or until the lentils are tender.
Add Greens (Optional):
If using spinach or kale, stir it into the soup during the last 5 minutes of cooking.
Season and Finish:
Remove the bay leaf and season the soup with salt, black pepper, and a squeeze of lemon juice to brighten the flavors.
Serve:
Ladle the soup into bowls, garnish with fresh parsley, and serve warm.