In a large pot, heat 3 Tbsp oil over high heat until shimmering.
Add onion and garlic. Saute until golden, about 4 min.
Stir in tomato paste, cumin, salt, black pepper, and chile powder. Saute another 2 min.
Add broth, lentils, and carrot. Bring to simmer, then cover and turn heat to medium-low.
Simmer until lentils are soft, about 30 min. Taste and add salt if needed.
Puree soup with immersion blender. Don't over-blend: soup should be somewhat chunky.
Stir in lemon juice and cilantro.
