Combine 1 ¼ cups all-purpose flour, ¼ cup sugar and ⅛ teaspoon salt in a large bowl and stir to mix well.
Scatter 5 tablespoons unsalted butter, cold and in small pieces and integrate with a pastry cutter or your hands until it’s the size of peas and beans, ensuring the mixture remains cool and powdery without becoming pasty.
Lightly beat 1 large egg and stir it in with a fork. Continue stirring until the dough holds together, then transfer it to a lightly floured surface and gather it several times until it comes together. Knead it briefly until smooth, but don’t overdo it as the more you touch it, the higher the chances the butter will start to melt and the crust will be tough when you bake it. So handle only as needed.
Shape it into a disk, wrap it in plastic, and refrigerate for at least 1 hour or unitl firm. At this point, you can keep it refrigerated for up to 3 days.
On a floured surface, roll the dough into a large circle about 13 inches in diameter. Fit it into a 9-inch pie pan with removable bottom that is at least 2 inches deep. If you don’t have one, you can use a springform cake pan the same size and have the dough reach halfway or ⅔ up the sides.
Press the dough well against the bottom and sides of the pan and trim the edges so they are even with the top of the pan. Chill the pan while preparing the filling.