Preheat your oven to 350°F (175°C).
In a large bowl, combine the blackberries, 1/2 cup of sugar, and lemon juice. Stir gently and set aside.
In another bowl, mix together the flour, baking powder, salt, and remaining sugar.
In a separate bowl, whisk together the milk, melted butter, and vanilla extract.
Combine the wet and dry ingredients until just mixed.
Pour the blackberry mixture into a greased baking dish.
Drop spoonfuls of the batter over the blackberries.
Bake in the preheated oven for 40-45 minutes, or until the topping is golden brown.
Let cool slightly before serving.
Serve warm with a scoop of vanilla ice cream on top.