To make the dough:

Cup of Yum
1. Preheat oven to 350°F and line a 9x13 baking dish with parchment paper.
2. In a standing mixer, add flour, sugar, and lemon zest. Mix until combined.
3. Add butter and continue mixing.
4. Stop the mixer and use your fingers or a fork to break up the butter into smaller pieces. Resume mixing.
5. Add eggs and continue mixing until a crumbly dough begins to form. Set aside.

To make the blackberry filling:

1. Add blackberries, lemon sugar, cornstarch and sugar to a large mixing bowl and stir together.

Build your blackberry crumble bars:

1. Press half of the dough into the bottom of the backing dish.
2. Pour blackberry mixture over the crust and speed with a rubber or silicone spatula until evenly distributed.
3. Crumble the remaining dough on top of the blackberry filling.
4. Bake for 35-40 minutes or until the crumble appears slightly golden brown.
5. Remove from oven and allow to cool completely before cutting.