Preheat the oven to 350°F (175°C). Grease the baking pan.

In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the flour and salt, mixing until combined. Press the mixture into the bottom of the prepared pan.

Bake for 15 minutes or until lightly golden.

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

Pour the filling over the baked crust.

Return to the oven and bake for an additional 20 minutes, or until the filling is set.

Allow to cool completely before slicing into bars.