Preheat oven to 300F°. Grease 8x8 inch square pan.
In a medium bowl, sift flour and salt together. Set aside.
Beat butter for 3-5 minute on medium high speed with paddle attachment until butter is light and fluffy. Turn down the speed of mixer, and slowly add the powdered sugar. Once sugar is mixed in, add in the flour and salt mixture, and only mix in for one to two minutes.
Transfer the batter to greased 8x8 pan. Using a parchment paper, or bottom of measuring cup to make a smooth even surface on top. Refrigerate dough for 30 minutes.
Bake 45-60 minutes. Visual cue for doneness is looking at the side of pan to see if the dough has separated for the edge of the pan. Top should be a light golden color. Allow to cool before cutting into pieces
Recommended cutting: three columns with 5 rows.