Place the rice in boiling water and leave for 5 seconds; drain, and rinse. Bring the milk almost to a boil in a heavy saucepan, and stir in the rice, the first quantity of sugar, the orange zest, salt, and butter. Reduce the heat to very low and simmer uncovered, stirring occasionally to prevent sticking, for 1 hour, or until thick and creamy. Remove from the heat and set aside.
Whisk together the egg, vanilla, lemon juice, and remaining sugar until pale and thick, about 2 minutes. Remove the orange zest from the rice mixture and stir half the rice into the egg mixture. Return this to the saucepan and stir to combine. Gently cook over low heat, stirring well, for 2 minutes. Stir in the Rich Cream and add more sugar or lemon juice if desired. (If using heavy cream, beat until slightly thickened, then stir into the rice mixture.) Divide among individual dishes and chill.
To serve, liberally dust with the cinnamon and confectioners' sugar.