Preheat oven to 450°F. Spray a 2 quart baking dish with cooking spray. Set aside.

In a large bowl stir together 1/2 cup sugar, flour, baking powder, cinnamon and salt. Cut in butter until mixture resembles pea sized crumbles. Stir in boiling water until just moist.

Combine blackberries, 1 cup sugar, cold water, cornstarch, and lemon juice in a medium saucepan. Bring to a boil over medium high heat. Reduce heat. Simmer until thickened about 5 minutes.

Pour blackberry filling into prepared baking dish. Drop spoonfuls of dough all over top.

Place baking dish on a foil lined baking sheet (to catch any potential overflow). Bake 25 minutes or until top is golden brown.

Remove from oven. Let cool 10 minutes. Serve with a side of vanilla ice cream or dollop of fresh whipped cream.