Preheat the oven to 375°F. Wash and peel the pear. Remove the stem and seeds, and grate the pear flesh.
Place the egg yolk in a bowl. Beat in lemon zest, cinnamon, and sugar. Mix in flour and milk; then stir in grated pear.
Whip the egg white to soft peaks using an electric mixer. Beat on high until, when you lift one of the beaters out of the bowl, the egg whites form small white peaks. Fold the egg white into the pear mixture.
Pour into a greased baking dish. Bake for about 30 minutes, or until pudding is set.
Allow to cool before serving.