Source: The Low Fat Jewish Cookbook by Faye Levy p. 269
Sort the lentils carefully, discarding any stones. Rinse lentils, then combine with the water in a large saucepan. Bring to a boil, cover and cook over medium heat about 20 minutes or until the lentils are just tender. Drain the liquid into a measuring cup, leaving the lentils in the pan and add enough water to make 3 cups.
In a heavy skillet, heat the vegetable oil over medium heat. Add the onions and saute, stirring occasionally, until they are well browned, about 15 minutes. Add the garlic and cumin and saute 30 seconds; reserve.
Add reserved lentil cooking liquid to pan of lentils and bring to a boil. Add salt and rice and return to a boil. Add the onion mixture. Cover, reduce heat to low, and cook, without stirring, until the rice is tender, about 20 minutes. Fluff gently with a fork. Season to taste with salt and pepper and lightly stir in parsley if desired. Serve hot.