Heat the olive oil in a large pot over medium heat. Add the onion, carrots, and celery. Cook for 5 minutes until the vegetables start to soften.
Stir in the garlic, cumin, and smoked paprika. Cook for 1 minute until the spices smell fragrant.
Add the rinsed lentils, diced tomatoes, and vegetable broth to the pot. Stir everything together.
Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for 30 minutes, stirring occasionally, until the lentils are tender.
Taste and add salt and black pepper as needed. Stir in the chopped parsley just before serving.