Beat 2 sticks butter, 1/2 cup granulated sugar and 3/4 cup confectioners' sugar until fluffy. Beat in 2 egg yolks, 1 teaspoon vanilla and 1 teaspoon orange zest. Whisk 2 1/4 cups flour, 1/2 teaspoon baking powder and 1/4 teaspoon salt; stir into the butter mixture, then chill 30 minutes. Roll tablespoonfuls into balls and flatten; sprinkle with coarse sugar and bake 15 to 20 minutes at 350 degrees.
Recipe courtesy Food Network Magazine, from 50 holiday cookies