Heat the olive oil in a large pot over medium heat.
Add the chopped onions and sauté until soft, about 5 minutes.
Stir in the garlic, carrots, and potatoes. Cook for another 5 minutes until fragrant.
Mix in the cumin and tomato paste, cooking for an additional minute.
Add the rinsed lentils and vegetable broth, bringing the mixture to a boil.
Reduce the heat, cover, and let it simmer for 20-25 minutes, or until lentils are soft.
Once the lentils are soft, season with salt, pepper, and lemon juice to taste.
Use an immersion blender to puree the soup to your desired consistency.
Serve warm, garnished with a drizzle of olive oil or fresh herbs if desired.