Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 5 minutes until it softens.
Stir in the minced garlic and smoked paprika. Cook for 1 minute until the spices smell fragrant.
Add the rinsed lentils, diced tomatoes, and vegetable broth. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 25 minutes until the lentils are tender.
Stir in the fresh spinach, salt, and black pepper. Cook for 3 more minutes until the spinach wilts.