Preheat oven to 350°F.
Line baking pan with foil, wrapping excess foil up and over the edges of the pan.
In a mixing bowl combine flour, softened butter and powdered sugar until a stiff dough forms.
Use your fingers to press dough into the bottom of foil lined 8 or 9 inch baking dish. Press dough ½ an inch up the sides of the pan.
Bake crust for 20 minutes.
While crust is baking prepare the lemon filling.
In the bowl of a stand mixer bowl, beat together the eggs, sugar, lemon juice, lemon zest, baking powder, and salt on high speed for about 3 minutes until light and frothy.
Remove crust once it has baked for 20 minutes.
Pour filling into hot crust and return tart to the oven.
Bake for another 30-45 minutes.
Test for doneness by lightly pressing the center of the tart with your finger. Tart is done when no indentation remains when touched lightly in the center.
Cool completely in the pan on a cooling rack for about 1 hour.
Carefully lift lemon tart out of the pan using the overhanging foil to assist. Then remove foil lining from underneath the tart.
Sprinkle with powdered sugar.
Cut into squares to serve.