Prepare the Pie Dough

Preheat your oven to 400°F (200°C).

Place the chilled pastry dough on a lightly floured surface. Using a floured rolling pin, roll the dough into a circle about 1 inch larger than your pie dish. Rotate the dough as you roll to prevent sticking.

Carefully transfer the rolled dough into a 9-inch pie dish. Gently press it into the bottom and sides to form an even crust.

Prepare the Streusel (Crumble Topping)

In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, brown sugar, granulated sugar, and salt on low speed. Add the oats and mix until everything is evenly incorporated.

Cut the chilled butter into small cubes and add it to the mixture. Mix on low to medium speed for about 3–5 minutes, until the mixture forms small, pea-sized crumbs. (It may look dry at first—this is normal, so keep mixing.)

Using your fingers, gently press the mixture together to form small clumps. Set aside.

Prepare the Filling

In a large bowl, combine the blueberries, lemon zest, and lemon juice. Stir gently to coat the berries evenly.

In a separate bowl, whisk together the sugar, flour, cornstarch, cinnamon, and salt.

Add the dry mixture to the blueberries and gently stir until all the berries are evenly coated.

Assemble and Bake the Pie

Pour the blueberry filling into the prepared pie crust.

Evenly sprinkle the crumble topping over the filling using your fingers.

Place the pie on a baking sheet and transfer it to the middle rack of the oven.

Bake for about 30 minutes, or until the topping begins to turn golden brown. Then loosely cover the pie with aluminum foil to prevent over-browning.

Continue baking for an additional 45–50 minutes, until the crust is golden and the filling is bubbling.

Remove the pie from the oven and allow it to cool completely for at least 3 hours before serving. This ensures the filling sets properly.