Preheat oven to 350 degrees and line a 9x13 baking dish with parchment paper
In a standing mixer, add the flour, sugar, and lemon zest and mix till combined.
Add in the butter and mix
Using your fingers or a fork, break up the butter into smaller pieces and mix
Add in the eggs and mix until a crumbly dough comes together
Press half of the dough into the bottom of the baking dish and set aside
In a large mixing bowl, combine the blackberries, lemon sugar, cornstarch and sugar and mix until combined
Pour the blackberry mixture over the crust and even it out with a rubber spatula
Crumble the remaining dough over the blackberry filling
Bake in the preheated oven for 35-40 minutes or until the crumble appears slightly golden brown
Pull the baking dish out of the oven and set aside to cool completely
Cut and enjoy!