Preheat oven to 425°. Prepare an 8x8 baking dish by spraying with a non-stick cooking spray.

Pour blackberry filling into the prepared baking dish. Make sure it is evenly spread in the dish.

In a large mixing bowl, add flour, sugars, baking powder, and salt. Whisk together until well combined.

Add in cubed butter and using a pastry cutter, cut butter into flour mixture until mixture becomes crumbly.

Pour boiling water and mix until ingredients and mixture becomes dough-like.

Spread topping mixture over blackberry filling, making sure to cover the entire dish with the topping.

Sprinkle the top of the cobbler with coarse sugar.