Serve this lattice-top tart warm with whipped cream or vanilla ice cream.
Lightly dust a clean work surface with flour; have ready a 9-inch fluted tart pan with a removable bottom.
Roll one disk of dough to an 11-inch circle, with an 1/8-inch thickness. Roll dough around rolling pin, and unroll over tart pan. Using your fingers, gently press dough into pan. Trim any excess dough flush with the edges of the pan, and chill 30 minutes.
Line a baking pan with parchment. Roll remaining disk of dough to an 1/8-inch thickness. Using a fluted pastry wheel, cut into 10 3/4-by-12-inch strips. Transfer strips to pan, and chill 30 minutes.
Peel, core, and cut each apple into 16 wedges. Place wedges in medium bowl; toss with lemon juice and rosemary. In a small bowl, combine sugar and cornstarch. Sprinkle sugar mixture over apples; toss to coat.
Heat oven to 400 degrees. Line crust with a 12-inch circle of parchment, and fill with pie weights or dried beans. Bake until crust starts to take on color, about 15 minutes. Remove weights and parchment. Reduce temperature to 350 degrees; continue baking until crust has cooked through, about 7 minutes.
Fill crust with apple mixture, and dot with butter. Using chilled strips of dough, weave lattice pattern over top.
Bake until lattice crust has slightly browned and apples are tender, about 1 hour. Remove from oven; transfer to a wire rack to cool. Decorate with glazed walnuts.