Mix dry ingredients in a large bowl then add cold butter pieces.

Use a pastry cutter to incorporate the butter until it is in little pea sized bits of butter and flour.

Sprinkle in 7 tbsp of cold water and mix.

Form a ball, it should stick together. Add 1 more tablespoon of water if necessary.

Pour the dough onto a cutting board, form a ball, then divide in half.

Make a ball with each half, flatten and cover each in plastic wrap.

Refrigerate for 1 hour or more before rolling.

Mix sugar, cornstarch, lemon zest, lemon juice, and salt in a large bowl.

Add blueberries and grated apple and combine well.

Roll out one crust to fit a 9 inch pie plate.

Add filling and top with the other crust.

Crimp the edges and cut slits so steam can escape.

Bake in a pre-heated 400° oven for 25 minutes, then turn temperature down to 350° and bake for an additional 25 minutes, until the filling starts to boil and the crust is nice and brown