1. Preheat oven to 350 degrees F. 2. Pour your melted butter in a 12 x 8 rectangular baking pan and set aside. 3. In a small bowl, make your blueberry topping. Mix together frozen blackberries, water and granulated sugar. Fold ingredients and set aside. 4. In another bowl, mix together flour, baking powder, salt, sugar and milk. 5. Pour the batter into your buttered pan and spread out evenly with a spatula. 6. Place your blackberries, one by one, on top of the batter. 7. Bake for 40 to 45 minutes.