Pour the milk into a large pot and bring to a boil. When it begins to boil, add the rice, the cinnamon stick, and the peel of lemon. Reduce the heat to low and simmer for about 50 minutes, stirring often. Add the sugar and cook for 10 more minutes. Stir well until the sugar is completely dissolved. Remove cinnamon stick and lemon peel. Remove from heat and pour rice pudding into a serving dish. Allow the rice mixture to cool down in the serving dish for 20 minutes, then refrigerate at least one hour. Sprinkle the top with ground cinnamon just before serving. Tip: Stir to avoid the layer of cream that appears when the pudding is getting cool. Serves 4.