Prepare Tart Pastry. Preheat oven to 450 degrees F. Wrap the rolled-out pastry around a rolling pin. Using pin, ease pastry into a 9-inch tart pan with removable bottom, taking care not to stretch the pastry. Press pastry into fluted sides of tart pan. Trim edges even with the pan. Line pastry with a double thickness of foil. Bake for 8 minutes. Remove foil. Bake 5 to 6 minutes more or until crust is golden. Cool on wire rack. Reduce oven temperature to 350 degrees F.
Meanwhile, finely shred 4 teaspoons peel from lemons. Set aside. Squeeze enough juice from lemons to measure 6 tablespoons; set aside.
In medium bowl combine sugar and flour. Add eggs. Beat with electric mixer on medium to high speed for 3 minutes or until mixture is light in color and slightly thickened. Stir in lemon peel, lemon juice, butter, and vanilla. Pour into pastry shell. Place tart pan on a baking sheet.
Bake 20 to 25 minutes or until filling is set and lightly browned. Cool on a wire rack.
To serve, remove sides of pan, and top tart with Oven-Candied Lemon Slices. Makes 8 servings.
Oven-Candied Lemon Slices
Line a 15x10x1-inch baking pan with parchment paper. Cut lemons crosswise into 1/8-to 1/4-inch-thick slices. Arrange in a single layer on pan. Sprinkle lemon slices with sugar. Bake in preheated 275 degree F oven 45 to 50 minutes or until lemons are almost dry and covered with sugary glaze. While still warm, loosen slices from paper to prevent sticking.
In medium bowl cut butter into flour until pieces are the size of small peas. In a small mixing bowl combine egg yolk, and 1 tablespoon ice water. Gradually stir the egg yolk mixture into the flour mixture. Add 2 to 4 tablespoons more water, 1 tablespoon at a time, until all the dough is moistened. Shape into a ball. If necessary, cover dough with plastic wrap and chill in refrigerator for 30 to 60 minutes or until dough is easy to handle. On a lightly floured surface, roll out dough on an 11-inch circle. Use to prepare Lemon-Vanilla Tart.