In a food processor, pulse together flour, 1 cup of sugar, baking powder, cinnamon, salt and lemon zest.
Add the butter, egg and vanilla extra. Pulsing until dough is crumbly. Lightly pat half of dough into the bottom of the prepared pan, saving the remaining dough for the topping.
In a medium bowl, stir together the remaining 1/2 cup sugar, cornstarch and lemon juice. Gently mix in the blackberries (if you wish smash some of the blackberries). Sprinkle the blackberry mixture evenly over the bottom crumble. Sprinkle the remaining crumble over the berry mixture.
Bake in preheated oven for about 35 - 40 minutes, or until top is slightly brown (you are only looking for the top to slightly brown, don't bake too long because the bottom will burn).