From Gourmet.
From Gourmet.
Preheat oven to 375°F.
Blend together butter, superfine sugar, zest, and salt in a bowl with a fork.
Sift flour into butter mixture and blend with fork until mixture forms a soft dough.
Transfer dough to an ungreased large baking sheet and pat into a 10- by 5-inch rectangle.
Prick dough all over with fork and sprinkle with coarse sugar (if using), pressing it gently into dough with your fingertips to adhere.
Score dough crosswise with back of a knife into 6 rectangles (do not cut all the way through), then score each rectangle into 2 triangles.
Bake shortbread in middle of oven until edges are golden but center is pale, 12 to 17 minutes.
Cool on baking sheet on a rack 10 minutes, then cut into 12 triangles along scored lines while still warm.
Transfer triangles with a long spatula to a rack to cool completely.
Shortbread can be made 3 days ahead and kept in an airtight container at room temperature.
Shortbread keeps 1 week.
