Step 1

Preheat oven to 350°F. Lightly grease an 8x8 baking pan.

Step 2

In a large bowl, gently stir together all filling ingredients. Transfer to the prepared pan.

Step 3

In a medium bowl, combine sugar, flour, baking powder, and salt. Add the vanilla extract and melted butter and stir until fully combined. The mixture will resemble a cross between a crumb topping and a sugar cookie dough.

Step 4

Press pieces of the topping together with your fingers to form flat irregular shaped pieces. Place the pieces of topping all over the top of the blackberries. Bake for 30-35 minutes, until the berries are bubbling and the topping is beginning to turn light golden brown. Place the pan on a wire rack to cool for about 15 minutes; the juices will thicken up a bit as it cools. Serve warm with vanilla ice cream.