In a medium bowl, whisk together the 1 1/4 cups flour, 1 tablespoon maple sugar, and salt. Add butter and work into dough so that the butter is down to pea-sized chunks. Add just enough water to incorporate as dough, smearing butter chunks in the process. Shape dough into a disk and shroud in plastic wrap; refrigerate for 30 minutes, or overnight.
Preheat oven to 350-degrees. Place parchment paper on a large rimmed baking sheet.
In a large bowl, gently stir together the vanilla (bean or extract), lemon juice, 2 tablespoons flour, and 1/2 cup maple sugar; it will form a thick paste. Gently stir in the pears to coat. Expect the mixture to become more liquid as it sits with the pears in it.
Use flour to lightly dust a large work surface. Roll out the dough to at least a foot diameter circle. Transfer it to the prepared parchment paper on baking sheet; the dough might hang over the edges for now, but that's okay.
Arrange the pears in a circular pattern in the center; leave a 2.5 to 3-inch border. Scrape the rest of the maple paste over the pears. Fold the dough inward, with the center still exposed. Brush the egg over the top and sprinkle on the maple sugar.
Bake for 40 to 50 minutes, until the crust is golden and the filling bubbles. Let cool before cutting.
OM NOM NOM!