Preheat your oven to 350ºF (177ºC). Lightly spray an 8” x 8” baking pan with a flour-based baking spray. For easier removal, place a parchment paper sling into the pan, securing with binder clips if necessary.
In a mixing bowl, using a hand mixer or a stand mixer with a paddle attachment, beat the butter, flour, and powdered sugar until it forms light yellow loose crumbs. Press this mixture into the bottom of the prepared pan and chill in the freezer or refrigerator for 10-15 minutes.
Bake the crust for 15-18 minutes or until light golden brown. Meanwhile, prepare the lemon curd.
For the filling, mix lemon juice, lemon zest, eggs, granulated sugar, and sifted flour with a mixer until well blended. Pour over the slightly cooled crust.
Return to the oven and bake for 25-30 minutes, until the top is nearly set with a slight jiggle in the center.
Allow to cool completely, then refrigerate for at least 1 hour or overnight. Dust with powdered sugar before serving.