Preheat your oven to 350°F (175°C).
In a mixing bowl, combine flour, powdered sugar, and softened butter.
Press the mixture into the bottom of a greased 8x8 inch baking dish to form the crust.
Bake the crust for 15 minutes until lightly golden.
In another bowl, whisk together granulated sugar, eggs, lemon juice, lemon zest, baking powder, and salt.
Pour the lemon mixture over the baked crust.
Bake for an additional 20 minutes until the filling is set.
Remove from the oven and allow to cool completely.
Dust with powdered sugar before cutting into squares.
Serve chilled or at room temperature.