In a large pot, heat olive oil over medium heat. Add the chopped onion, carrots, and celery. Sauté for about 5-7 minutes until the vegetables soften.
Stir in the minced garlic, cumin, coriander, and smoked paprika. Cook for another 2 minutes until fragrant.
Add the rinsed red lentils and diced tomatoes (with their juice) to the pot. Stir everything together.
Pour in the vegetable broth and bring the mixture to a boil. Reduce the heat to low, cover, and let it simmer for about 25-30 minutes or until the lentils are tender.
Once the lentils are cooked, stir in the chopped spinach and cook for an additional 5 minutes. Season with salt and pepper to taste.
Remove from heat and let the soup cool slightly before serving.
Notes
Serve the soup in warm bowls, garnished with fresh cilantro or parsley, and drizzle a touch of olive oil on top for extra flavor.