1 cup butter (2 sticks), softened (no substitutions)
1/2 cup confectioners' sugar
2 cups all-purpose flour
1/4 teaspoon baking powder
Preheat oven to 325 degrees F. Line 9" by 9" metal baking pan with foil.
In large bowl, with mixer at medium speed, beat butter and sugar until creamy, occasionally scraping bowl with rubber spatula.
With hand, mix flour and baking powder into butter mixture just until crumbs form. (Do not overwork dough or shortbread will be tough.) Pat crumbs into baking pan. With fork, prick dough all over in a decorative pattern.
Bake shortbread 35 to 40 minutes, until lightly browned around the edges. Cool in pan on wire rack 10 minutes.
Transfer with foil to cutting board. While still warm, cut shortbread into 3 strips, then cut each strip crosswise into 8 pieces. Cool pieces completely on wire rack. Store cookies in tightly covered container up to 1 week.
