Melt butter in a microwavable dish.
Pour 1 cup of sugar, flour, baking powder, and salt into a mixing bowl, whisking in milk. Mix well.
Then, pour in melted butter and whisk it all together.
Butter a baking dish. Rinse and pat dry the blackberries.
Pour the batter into the buttered baking dish.
Sprinkle blackberries over the top of the batter; distributing evenly.
Sprinkle ¼ cup sugar over the top.
Bake in the oven at 350°F for 1 hour, or until golden and bubbly.
If you desire, sprinkle an additional teaspoon of sugar over the cobbler 10 minutes before it’s done.
