Oven Preparation: Preheat your oven to 375°F (190°C), positioning the rack in the center.
Prepare the Crumble: In a large bowl, whisk together flour, sugar, baking powder, and salt. Using a pastry cutter or your fingers, work the butter into the flour mixture until it resembles coarse crumbs. Stir in vanilla, egg, and apple cider vinegar until the dough forms and there are no dry flour patches left.
Form the Base Layer: Transfer half of the crumble mixture into a 2-quart baking dish or a deep-dish pie pan. Spread it out to cover the bottom and press down gently to form a compact layer.
Mix the Filling: In a separate bowl, toss the blackberries with sugar and cornstarch until evenly coated. Mix in lemon juice and zest. Pour this berry mixture over the prepared base in the baking dish, spreading it out evenly.
Add the Top Layer: Crumble the remaining dough over the blackberry filling, lightly pressing some of the dough together to create small clumps for texture.
Bake: Place in the oven and bake for 40-45 minutes, or until the topping is lightly browned and crisp.
Cool and Serve: Allow the blackberry crumble to cool on a wire rack for about 30 minutes. Serve warm, ideally with a scoop of vanilla ice cream on top.
Enjoy this delightful Blackberry Crumble, a perfect balance of tart blackberries and sweet, buttery crumble. It’s an ideal dessert for any season, offering a comforting and satisfying treat.