Preheat oven to 400°F.
To make crust, combine flour, 1/4 cup sugar and 1 tablespoon lemon peel in medium bowl.
Cut in butter until mixture resembles coarse crumbs.
Stir in egg yolk, vanilla and 1 teaspoon lemon juice.
Press evenly in 9-inch pie plate; trim and flute edge.
Prick dough and line with foil.
Fill with dried beans, uncooked rice or pie weights and bake 10 minutes.
Remove foil lining and beans; cool completely on wire rack.
To make filling, beat 4 egg yolks in small bowl.
Combine with 1/2 cup of the sugar, 1/3 cup lemon juice, 2 tablespoons lemon peel and the gelatin in top of double boiler.
Cook over boiling water 5 minutes or until thickened, stirring constantly.
Remove from heat.
Beat egg whites and salt in large bowl until soft peaks form.
Gradually add remaining 1/2 cup sugar, beating until stiff and glossy.
Fold egg white mixture into lemon mixture; pour into cooled crust.
Refrigerate until set.
Garnish with whipped cream and lemon peel.