Preheat oven to 350.
Spray a 9×13 baking pan with non-stick pan spray.
Spread the blackberries in the bottom of the prepared pan.
4 Cups (576 g) Blackberries
Cover the berries evenly with sugar.
1 Cup (200 g) Sugar
Sprinkle the cake mix over the blackberries and sugar. Do not press or stir.
1 box Cake mix
Sprinkle the water over the cake mix to moisten it.
1 Cup (236.59 g) Water
Drizzle the melted butter over the remaining dry parts of the cake mix.
½ Cup (113.5 g) Butter
Crumple the brown sugar over the cake before covering with foil.
⅓ Cup (73.33 g) Brown Sugar
Cover with foil and bake for 45 minutes. Remove foil and bake an additional 15 minutes or until the top of the cake is golden brown and crunchy.
Remove from the oven and serve with ice cream and/or whipped cream.