Preheat oven to 400 degrees. Beat sugar with flour, milk, egg yolks, and lemon peel until smooth. Toss pear slices with lemon juice in a large bowl. Add milk mixture and mix until pears are well coated. Pour into pie crust, cover the edges with foil, and bake for 20 minutes or until pears are tender.

In a medium bowl, beat egg whites with vanilla using an electric beater on medium speed until foamy. Gradually add sugar, one tablespoon at a time. Beat on high speed after each addition until sugar is completely dissolved. Spread meringue mixture over pear filling in pie and bake inside oven at 350 degrees until top is golden brown. Set pie aside to cool.