In a large bowl, mix the flour and salt. Cut in the cold butter until the mixture is crumbly. Gradually add ice water until dough forms. Divide into two discs, wrap, and chill for 30-60 minutes.
Preheat oven to 350°F (177°C). Roll out one dough disc on a floured surface into an 11-inch square, place it in an 8×8 square pan, trim excess, and prick with a fork. Line with foil and pie weights, and bake for 10-12 minutes.
Combine blueberries, sugar, lemon zest, and cornstarch. Remove crust from oven, remove weights, and add filling.
Roll second dough disc, cut into strips, and weave over the filling to form a lattice. Trim excess dough. Brush with egg wash, sprinkle sugar, and bake for 40-50 minutes until golden.