01 - Preheat oven to 375°F. Lightly grease a 9x9-inch baking dish with butter or cooking spray.
02 - In a large bowl, combine frozen blueberries, granulated sugar, cornstarch, lemon juice, ground cinnamon, and salt. Toss until berries are evenly coated. Pour mixture into prepared baking dish and spread into an even layer.
03 - In a separate bowl, whisk together flour, sugar, baking powder, baking soda, and salt until well combined.
04 - Pour melted butter, milk, and vanilla extract into the flour mixture. Stir gently until just combined—batter will be thick and slightly lumpy. Avoid overmixing to prevent tough texture.
05 - Drop spoonfuls of batter evenly over the blueberry filling, covering most of the surface. Leave small gaps for steam to escape and fruit juices to bubble through during baking.
06 - Bake for 40 to 45 minutes until topping is golden brown and set, and berry filling is bubbling vigorously around the edges.
07 - Let cobbler rest for at least 15 minutes before serving to allow filling to set slightly. Serve warm with vanilla ice cream or whipped cream.