Heat oven to 350 degrees F.
In large bowl combine dry ingredients. Add butter and stir mixture with a fork until a soft dough forms. Divide dough in half. Press evenly in bottom of two 8-inch cake pans that have been very lightly sprayed with nonstick vegetable spray and then wiped out. Spread dough disks to about 7-½ inches wide and flute the edge with a spoon or finger.
Prick all over with a fork, then score with a sharp knife into small squares, being careful not to cut all the way through. Bake until light golden brown, 20 to 30 minutes. Cool on wire rack and serve or store.