In a large cast iron casserole or soup pot, heat the oil over medium heat. Add the chopped shallot and cook for 2–3 minutes until softened. Add the garlic and chopped tomato, and sauté for 5 more minutes until the tomato starts to break down.
Stir in the diced carrots and red bell pepper. Let everything cook together for another 5 minutes. This aromatic mix is the heart of the soup.
Rinse the lentils and add them to the pot along with the coriander bouquet, salt, water, and vegetable stock. Stir well and bring to a boil.
Lower the heat to a gentle simmer and cook uncovered for about 35 minutes, or until the lentils are soft but still hold their shape. Stir occasionally and add more hot water if needed. Taste and adjust salt as desired.
Ladle the soup into bowls and top with crumbled queso fresco and a dollop of sour cream. Serve hot with warm tortillas.
