Preheat your oven to 350°F (175°C).
In a bowl, combine blackberries, 1/2 cup of sugar, lemon juice, and vanilla extract.
Spread the blackberry mixture evenly in a greased baking dish.
In another bowl, whisk together flour, baking powder, salt, and remaining sugar.
Add the milk and melted butter to the dry ingredients, stirring until just combined.
Drop spoonfuls of the batter over the blackberry mixture.
Sprinkle with cinnamon if desired.
Bake in the preheated oven for 35-40 minutes, until the top is golden brown.
Let it cool slightly before serving.
Enjoy warm, optionally with a scoop of vanilla ice cream!