Lemon Squares

Why I Love This Recipe
While not a Martha Stewart fanatic, I haven't tasted better lemon squares than hers. Sweet and delicious! These always remind me of cooking with my mother.
Ingredients You'll Need
1 cup all-purpose flour, sifted
1/4 cup confectioners' sugar, sifted, plus more for dusting
6 tblsp unsalted butter, chilled and cut into tablespoon-size pieces
3 large eggs
1 1/2 cups granulated sugar
Grated zest of 1 1/2 lemons
1/2 cup freshly squeezed lemon juice (3-4 lemons)
Cornstarch in case the filling is too thin -- eyeball it
Directions
Heat oven to 325 degrees.
In a medium bowl, combine 3/4 cup flour and confectioners' sugar. Using a pastry cutter or your hands, cut in butter until mixture resembles coarse meal. Gently pat into an 8- or 9-inch glass baking dish, and bake until crust is golden brown, 20 to 25 minutes. Transfer dish to a rack to cool.
Reduce oven to 300 degrees.
Whisk together eggs and granulated sugar in a medium bowl. Add lemon zest and juice, and combine. Sift in remaining 1/4 cup flour and stir to combine. Add cornstarch if filling is too thin. Pour filling onto baked crust, and bake until filling sets, about 40 minutes. Refrigerate until well chilled before slicing, 1 hour and preferably overnight. Dust with confectioners' sugar, slice into pieces with a sharp knife, and serve.