In a saute pan with a lid, heat the olive oil over medium heat. Add the diced onion and saute until soft and translucent, about 8 minutes. Stir in the lentils and stock and bring to a boil. Reduce the heat and cover - cook for about 10 minutes. Stir in the rice and cover again - cook until both the rice and lentils are tender and the liquid is absorbed, another 10 - 15 minutes.
This is traditionally served topped with yogurt and fried onions. To make the fried onions, saute sliced onions in vegetable oil over high heat for 10 minutes or until well-caramelized, almost burnt.