Preheat the oven to 375 degrees.
Prepare your pie or pastry dough and roll out into a 12" circle on a parchment lined baking sheet.
TIP: Crushed cookies or an egg wash are recommended to cover the dough before adding the fruit mixture so that the fruit will not create a "soggy bottom" of the crust after baking. This is especially helpful if using blueberries from the freezer.
Combine together blueberries, 1 T sugar and 1 1/2 T flour, and the lemon zest and juice in a large bowl.
Pour the blueberry mixture into the center of the dough into a mound leaving an inch and a half border around the edge of the dough.
Combine the 4 T butter, 1/4 C flour and 1/4 C sugar together in a small bowl for the crumble using a fork or a pastry blender.
Add the crumble over the blueberry mixture evenly.
Fold the dough up over the edge of the blueberries and pinching to make pleats. Brush the pleated dough with a bit of egg wash or heavy cream and a pastry brush.
Sprinkle granulated sugar over the top of the galette.
Bake in a preheated oven for 25 minutes or until the crust is golden brown.