Preheat the oven to 350°F (175°C).

In a mixing bowl, combine flour, sugar, and salt.

Add softened butter and mix until crumbly.

Press the mixture into the bottom of the baking pan.

Bake for 15 minutes or until lightly golden.

In a separate bowl, whisk together sugar, eggs, lemon juice, lemon zest, flour, and baking powder until smooth.

Pour the filling over the baked crust.

Bake for an additional 20 minutes, or until the filling is set.

Allow to cool, then cut into squares and dust with powdered sugar if desired.