Combine flour, cold butter, and caster sugar in a food processor and pulse until coarse breadcrumbs form. Gradually add ice water until dough forms. Shape into a disk, wrap, and refrigerate for 30 minutes.

Preheat oven to 180°C (350°F). Roll out dough and fit it into a pie dish, dock the bottom, and blind bake covered with parchment and weights for 15 minutes.

Mix sliced apples with brown sugar, cinnamon, and lemon juice. Let sit for 15 minutes, then stir in flour and salt to thicken.

Pour apple filling into the cooled crust, heaping slightly in the center.

Combine crumb topping ingredients until resembling coarse crumbs. Sprinkle over apple filling.

Bake pie for 45-60 minutes until golden brown. Tent with foil if topping browns too quickly.

Cool at room temperature for 30 minutes before serving.