Preheat the oven to 350 degrees F.
For the crust: In a food processor, combine the confectioners' sugar, flour, and butter, and process until the mixture forms a ball. With your fingers, press the dough into a 12-inch tart pan with a removable bottom, taking care to push the crust into the indentations in the sides. Pat until the crust is even. Bake for 10 to 12 minutes, until very lightly browned. Set aside to cool.