1. Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish to prevent sticking.
2. In a large bowl, combine the blackberries, 1 cup of sugar, cornstarch, lemon juice, and lemon zest. Toss gently until the berries are evenly coated.
3. Pour the blackberry mixture into the prepared baking dish, spreading it out evenly.
4. In a separate bowl, whisk together the flour, 1 cup of sugar, baking powder, and salt. Stir in the milk, melted butter, and vanilla extract until you have a smooth batter.
5. Pour the batter evenly over the blackberry mixture. It’s okay if it doesn’t cover completely; the batter will spread as it bakes.
6. Bake in the preheated oven for 45-50 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
7. Let the cobbler cool for at least 15 minutes before serving. This allows the juices to thicken slightly, making it easier to scoop.

Remember, baking is all about patience. Resist the urge to open the oven door too often, as it can affect the baking process. Trust the process and enjoy the delightful aromas filling your kitchen!