Preheat the oven to 350 degrees F. Spray a 9x13 inch baking dish with nonstick spray.
In a small bowl, rub the sugar together with the lemon zest for the crust. You want the lemon zest distributed all through the sugar.
Stir the flour, lemon sugar and salt together in a large bowl. Add the melted butter and stir until a shortbread-like dough comes together. I even use my hands to bring it together. This may take a minute or two. Press half of the dough into the bottom of the dish.
In another bowl, make the filling. Whisk together the eggs, half and half, sugar, lemon zest and juice, vanilla, salt and cornstarch. Gently fold in the berries.
Pour the mixture over top of the crust.
Crumble the rest of the crust/shortbread over top of the blueberry mixture. Bake for 40 to 45 minutes, until the bars are set and no longer jiggly.
Cool completely before slicing into squares! You can also chill these in the fridge overnight before slicing.