Preheat the oven to 425° F. Line a 8"x8" brownie pan with two sheets of overhanging parchment (this will make it easy to lift the pie out of the pan).

In a large mixing bowl, whisk together the flour and salt. Add the butter cubes, tossing it in the flour to coat. Rub the butter into the flour, pinching the cubes with your thumb and forefinger so they form walnut-sized discs (for a flaky crust).

Make a well in the center, and add the water a few tablespoons at a time and mix just until the dough comes together, pulling flour into the well from the sides.

Form the dough into a small square, then wrap and chill for at least 30 minutes. 

Roll out chilled pie dough on a lightly floured surface. Transfer it to the brownie pan, folding any overhanging dough downwards to create a thick outer crust. Chill until ready to use. 

Mix all the ingredients in a bowl, making sure that every blueberry is coated.

In a medium bowl, stir together the sugar, flour, baking powder, salt, and zest from one lemon. Use a fork or pastry cutter to blend in the butter and egg. Crumble the mixture into big and small crumbles. 

In a separate small bowl, mix the turbinado sugar and zest from one lemon until the sugar is moistened.

Add the filling to the prepared crust. Crumble the crumb topping on top and then sprinkle the sugar and lemon zest mixture on top. Bake for 40 minutes or until golden brown.