Preheat the oven to 350°F (175°C). 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 a greased 9x9 inch baking dish.

Bake the crust for 20 minutes or until lightly golden.

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

Pour the filling over the baked crust and return to the oven.

Bake for an additional 15 minutes, or until the filling is set.

Allow the lemon bars to cool completely in the baking dish before cutting into squares.

Dust with powdered sugar before serving, if desired.