The night before: Strain the pears reserving the liquid for the glaze later. Cover and place liquid in fridge.
Mix lemon juice, whiskey, sugar, and vanilla in a bowl, toss pears in this mixture, and refrigerate overnight. In a food processor, blend sugar, flour, salt, and butter until the dough forms. Chill the dough overnight.
On the day of baking, roll out the dough, place it in a tart pan, and freeze for 30 minutes. Preheat the oven to 375°F, bake the tart shell with weights, and let it cool.
Meanwhile, cream butter and almond paste, add egg, cornstarch, and whiskey. Spread this filling into the tart shell. Slice and arrange the drained pear halves on top. Bake until golden brown.
Make a glaze from pear and whiskey liquid, and brush it over the tart. Serve immediately or store wrapped for up to three days.