3/4cup(1 1/2 sticks) unsalted buttersliced and softened
Preheat oven to 325°F.
Measure flour, 1/4 cup granulated sugar, powdered sugar, and salt into the bowl of a large food processor. Pulse until blended. Add butter and pulse in long pulses until the mixture resembles coarse sand.
Pour the mixture onto a lightly floured board and, with floured hands, gently form it into a ball. Press dough into the bottom of an ungreased 9-inch baking pan with a removable bottom, or a 9-inch springform pan. Use the tines of a fork to make impressions around the border of the dough, and then evenly prick the surface. Sprinkle with the remaining 1 tablespoon of sugar.
Bake for 35 to 40 minutes or until pale golden brown with a firm center. Remove from the oven and cut into 8 to 12 wedges with a sharp knife. Allow to cool completely before removing sides of pan and lifting out cookies. Store in an airtight container.
If you don't have a food processor, you can easily make this recipe by hand by whisking the dry ingredients together in a large bowl and then cutting in the softened butter using a fork or pastry cutter until mixture is very crumbly with no large particles remaining. From there, follow the rest of the above recipe.