Combine the flour, softened butter, and confectioners’ sugar in a bowl until the mixture forms a soft dough. Press this mixture evenly into the bottom of an ungreased square baking pan to form the crust.
Place the pan in a preheated oven at 350°F and bake until the crust is lightly golden and set.
While the crust bakes, beat the eggs in a small bowl. Add the sugar, flour, baking powder, lemon juice, and lemon zest, mixing until the filling becomes smooth and slightly frothy.
Pour the filling evenly over the hot crust, spreading gently so it reaches the corners.
Return the pan to the oven and bake until the filling is set and lightly golden on top.
Remove from the oven and allow the bars to cool completely on a wire rack. Once cooled, dust generously with confectioners’ sugar and cut into squares before serving.