Prepare the tart crust by processing the shortbread cookies in the food processor until very fine. Add to the processor the butter. Pulse until evenly moistened.
Spoon some of the crumb mixture in the tart pan. Using the straight side of a measure cup, press the crumbs up the sides of the tart pan being sure to tightly press into the grooves to 1/4” thick. Using the bottom of the measure cup, press the remaining crumbs into the bottom of the tart pan.
Carefully place tart crust into the refrigerator to chill while preparing the Frangipane.
For the Frangipane, in the drum of the food processor, process together the almond paste and sugar to break it apart. Add in the butter. Mix in the egg, flour, salt, and almond extract and process until light and fluffy. There will be very little filling initially, as the frangipane will give rise during baking, filling in the gaps between the pear slices.
Peel and core the pear, and then slice thinly, about 1/8 to 1/4-inch thick. Places the slices in a bowl with the lemon juice to help preserve their color.
Spread the frangipane over the bottom of the tart crust using a rubber spatula and an extra light hand. Next, carefully arrange the pear slices in a decorative pattern. They can slightly overlap, but don't build them up in layers or the tart will lack a refined appearance after the bake.
Bake at 375°F for 30-35 minutes or until the pears take on a bit of color and the edges of the tart shell are golden brown. Cool on a wire rack.
While the tart bakes, place the apricot jam, lemon peel, vanilla extract, and Riesling into a small saucepan and warm over medium heat for 5 to 8 minutes, constantly stirring. Once the mixture has reduced and thickened, take it off the heat and set it aside.
Once the tart is out of the oven brush the apricot glaze over the pears. Serve.