Add flour, sugar, and salt to the bowl of a food processor. Pulse a few times to combine. Cut the cold butter into cubes. Add to the flour mixture along with the vegetable shortening. Turn processor on and let run for 5 seconds. Then, drizzle in cold water. Keep processing until mixture begins to clump.
Pour dough mixture onto a clean surface. Using your hands, pull the dough together into one ball and then form into a disc. Cover disk in plastic wrap. Refrigerate until cold, at least 2 hours.
Remove disc of dough from the refrigerator and let it sit on the counter for 10 minutes to soften up. Preheat oven to 375 degrees.
Once dough is ready, roll it out into a disk using a rolling pin. The dough should be 10½ to 11 inches in diameter. Gently fold rolled dough in half and place onto 9-inch tart dish. Unfold the dough so that it is covering the dish completely. Let the dough lay into the dish so that it is not stretched or pulled. Using a rolling pin, push dough into the edges of the tart dish to neatly break off the excess dough.
Place a sheet of parchment paper over the tart shell and fill with one layer of pie weights or dry beans. Place onto baking sheet and then into preheated oven and bake until shell is dry, about 20 minutes. Remove from oven and reduce temperature to 350 degrees.