In a medium bowl, whisk the eggs, sugar and zest, then whisk in the flour and salt. Stir in the lemon juice, milk and butter, blend well.
Reduce the oven temperature to 325 degrees F when you remove baked crust from oven. Stir the filling one more time and pour onto the hot crust. Bake until the filling feels firm when touched lightly, about 20 minutes. Do not overbake.
Transfer pan to a cooling rack and cool until almost at room temperature, about 30 minutes. Pull the long sides of the parchment paper to remove the entire bar from the pan onto a cutting board. Cut bars as desired.