In a pot over medium heat, add the lentils, potato, and carrot. Pour in the water and bring to a boil. Let it cook for 15 minutes.

In a skillet over medium heat, add the oil and sauté the onion until it softens and turns golden.

Add the sautéed onion to the lentil mixture and stir. Use an electric blender to puree the mixture until smooth and creamy.

Add the salt and cumin, stir, and let it simmer for another 10 minutes. Serve hot.