- In a large pot, heat 3 tablespoons oil over high heat until hot and shimmering.
- Add onion and garlic, and sauté until golden, about 4 minutes.
- Stir in tomato paste, cumin, salt, black pepper and chili powder or cayenne, and sauté for 2 minutes longer.
- Add broth, 2 cups water, lentils and carrot. Bring to a simmer, then partially cover pot and turn heat to medium-low. Simmer until lentils are soft, about 30 minutes. Taste and add salt if necessary.
- Using an immersion blender, purée half the soup then add it back to pot. Soup should be somewhat chunky.
- Reheat soup if necessary, then stir in lemon juice and cilantro.
- Serve soup drizzled with good olive oil and dusted lightly with chili powder if desired.