Lemony Cookie Bars

⁄2 plus 1⁄4 cups all-purpose flour (divided use)

plus 11⁄2 cups powdered sugar (divided use)

⁄4 teaspoon salt (divided use)

⁄4 cup butter (cold and sliced in pieces)

eggs

⁄4 cup fresh lemon juice

⁄2 cup nonfat plain Greek yogurt

⁄2 teaspoon baking powder

lemon zest

Extra powdered sugar (for sprinkling)

organic blueberries for topping (optional)