Heat ghee in a heavy bottomed pan and fry the chopped onion till crisp. Remove from ghee and keep aside. Add the cooked rice and saute for two minutes. Add lime juice and salt to the grated apples and mix lightly. Add the seasoned apples to the cooked rice and mix lightly. Add honey, nutmeg powder and saffron to the rice and keep stirring on low heat for five minutes. Serve hot, garnished with walnuts.