In a medium stockpot over medium heat, add the oil, onion, garlic, and carrot. Cook for about 7 minutes, until fragrant.
Then, add the lentils, thyme, and water. Bring to a boil, then cook over medium low for about 25 minutes, or until all water is absorbed. (You can drain off excess water if needed).
Squeeze fresh lemon juice over the lentils and season with salt to taste.