In a large pot, heat 2 Tbsp unsalted butter over medium.
Add 1 medium yellow onion, 1 cup diced carrots, 1 cup diced celery, 4 cloves garlic, 1 tsp smoked paprika, and ½ tsp each salt, pepper, ground coriander, and cumin. Cook until onion is soft and fragrant, about 5 minutes.
Add 8 cups vegetable broth, 1 28-oz can crushed tomatoes, and 1 lb pound brown lentils. Cover and simmer, stirring occasionally, for 30 to 45 minutes, or until lentils are soft.
Before serving, squeeze in fresh lemon juice and stir. Serve with grated parmesan, Italian parsley, and crusty bread.
