Preheat oven to 350°F. Combine flour, powdered sugar and salt in a bowl and then cut in butter until the mixture has a coarse crumb texture. Press into a lightly greased 13x9€? pan; bake for 15 to 20 minutes or until very lightly browned. While baking, beat filling ingredients together in a large bowl. Remove crust from oven, pour filling over crust and bake for another 25-30 minutes or until filling is set. Remove from oven, cool, dust with powdered sugar, if desired and cut into bars.
