Simmer the lentils in water for about 45 minutes, uncovered, or until tender. Drain.
While lentils cook, heat olive oil in a pan over medium heat, and saute the parsley and the garlic. Cook briefly, and then add the rice. Saute for about a minute. Disolve the tomato paste in the stock and add that mixture to the rice. Season with salt and pepper. Bring to a boil, and then reduce heat, cover, and simmer slowly till rice is tender, about 25 mintues. When rice is done, adjust seasonings and add the lentils. Mix and serve.