Whisk together flour, sugar, baking powder, and kosher salt.
Mix in melted butter, egg, and lemon zest.
Press the dough into a prepared pan, making sure to reserve 1 ¼ cups.
Bake until the edges are golden-brown and let cool while making the filling.
Beat cream cheese, sugar, egg, and lemon zest until smooth.
Spread the mixture over the crust, then sprinkle the reserved crust mixture evenly over the filling.
Bake until the center is just slightly jiggly.
Let cool completely before cutting into bars.
