Step 1

Preheat oven to 300 degrees, with rack in upper third. Sift flour and salt into a bowl; set aside. Put butter into the bowl of an electric mixer fitted with the paddle attachment. Mix on medium-high speed until fluffy, 3 to 5 minutes, scraping down sides of bowl. Gradually add sugar; beat until pale and fluffy, about 2 minutes.

Step 2

Reduce speed to low. Add flour mixture all at once; mix until just combined.

Step 3

Butter a 10-inch round springform or cake pan. Using plastic wrap, press dough evenly into pan. With plastic on dough, refrigerate 20 minutes.

Step 4

Cut dough into 8 wedges with a paring knife. Using a wooden skewer, prick all over at 1/4-inch intervals.

Step 5

Bake until golden brown and firm in center, about 1 hour. Transfer pan to a wire rack. Recut shortbread into wedges; let cool completely in pan. Can be stored in an airtight container up to 2 weeks.