1. Set the oven rack to the middle position and preheat the oven to 425 degrees Fahrenheit.
2. To make the crust, pulse the flour and salt in a food processor for a few seconds to combine. Scatter the pieces of margarine over the flour mixture and pulse about 15 times, until the mixture resembles a coarse yellow meal and no white powdery bits remain. Turn it out into a large mixing bowl and pour in the beaten egg and water. Fold with a rubber spatula until the dough sticks together.
3. Form the dough into a disk and roll it out on a generously floured surface to an 11-inch circle. Be sure to flour the top of the dough thoroughly as well, as it will be sticky. Brush off the excess flour and transfer to a 9-inch pie plate. If the dough sticks, use a bench scraper or knife to ease it off. If it tears, you can fix it in the pan by pressing the torn pieces together, using a little water as glue if needed. Line the crust with aluminum foil and weigh it down with beans or coins (or pie weights, if you have them!). Bake for 25 minutes, then remove from the oven and reduce the heat to 400 degrees Fahrenheit.