Preheat your oven to 350°F (175°C). In a mixing bowl, combine blackberries, sugar, flour, lemon juice, and vanilla extract. Gently toss to coat the berries and set aside.

In another bowl, whisk together flour, sugar, baking powder, and salt. Stir in the milk and melted butter until just combined.

Pour the blackberry mixture into a greased baking dish. Spoon the topping over the blackberries evenly. Bake for 30-35 minutes or until the topping is golden brown and a toothpick inserted comes out clean.

Let the cobbler cool for a few minutes before serving. Enjoy warm, optionally with a scoop of vanilla ice cream.