In a large bowl, put flour, sugar, salt and mix by hand. Cut the butter into small pieces and by using your finger, mix together until it comes together to the size of small peas.
Sprinkle the ice water and gather with your hand. Add more water a tablespoon at a time until the dough is moist but not wet.
Divide the dough into 2 and shape into discs. Wrap in plastic wrap and refrigerate for 1 hour or overnight. Before rolling out the dough, leave out on your countertop for about 10 minutes.
On a lightly floured surface, roll out one dough to the size of the baking pan. Fit into the tart pan and trim the excess dough. Refrigerate while cutting the second crust into strips.
Roll out the second dough on a lightly floured surface. Cut into strips with pastry cutter.
Filling
Preheat oven to 400 degrees Fahrenheit. In a large bowl, combine the peaches, sugar, cornstarch, and lemon juice together. Pour into the the baking pan.
Put little pats of butter on top of the peaches.
Make the lattice pattern on top with the strips of the crust. Trim the excess dough by cutting the excess crust.
Brush the top with the egg wash. Sprinkle with the sugar.
Bake for 35-40 minutes. Remove from oven and let cool before cutting it.