In a pot over medium heat, add plenty of water and the red lentils. Bring to a boil and cook until the lentils are tender.

In a skillet, heat the oil. Add the finely chopped onions and cook until they turn a deep reddish color. Add some of the lentil cooking water to the onions, mash them slightly, and let simmer for a few minutes. Then add the onion mixture to the cooked lentils.