In a medium bowl whisk together flour, cornstarch, powdered sugar, salt and baking powder, add vanilla, butter cut in pieces (till resembles coarse crumbs) then add zest of the lemon, and yogurt, mix together to form a soft smooth dough.
On a lightly floured flat surface roll dough to 1/4 inch (1/2 centimeter) thickness and cut into desired shapes. Place on parchment paper lined cookie sheets and bake for approximately 10 to 12 minutes. Let cool completely. Enjoy!