Roll out the chilled pie dough on a lightly floured surface to about ⅙ inch thick. Fit it into a 9-inch glass pie dish, leaving about ½ inch overhang. Trim and crimp or flute the edges. Chill the lined crust in the refrigerator for at least 30 minutes.

Preheat the oven to 425°F (220°C). Use a fork to prick the bottom and sides of the crust to prevent puffing.

Line the crust with parchment paper and fill it with pie weights, dried beans, or uncooked rice. Ensure the weights reach the top edge of the crust.

Bake for 10 to 15 minutes, or until the edges are lightly golden. Carefully remove the weights and parchment.

Prick the bottom of the crust again and return to the oven for 2 to 3 minutes, until it looks dry.

Add blackberries, sugar, lemon juice, cinnamon, and salt to a saucepan. Cook over medium heat for 8 to 12 minutes, stirring often.

Mix cornstarch and cold water to make a slurry, then add to the berries. Cook for 1 to 2 minutes until thick and bubbling. Let cool.

In a bowl, combine flour, sugar, cinnamon, baking powder, and salt. Rub in the cold, cubed butter until crumbly.

Spread blackberry filling into the par-baked crust and sprinkle crumble evenly on top.

Bake at 350°F (180°C) for 35 to 40 minutes, until crumble is golden and filling bubbles.

Cool the pie completely so the filling can set. For clean slices, cool for at least 4 hours or chill in the fridge.

Store leftovers in the fridge for up to 3 days.