(optional) Saute onion in liquid of your choice for 2-3 minutes or until tender. Stir in the water, juice, lentils, and bay leaf; bring to a boil. Reduce the heat to low; cover, and simmer for 30 to 45 minutes, or until the lentils are soft but not mushy. Remove the pan from the heat and discard the bay leaf. Stir in the couscous, tomatoes, basil, and Parmesan. Cover and let stand for 5 minutes or until the couscous is soft. Uncover and fluff with a fork to separate the grains, serves 4.