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 with sugar, cornstarch, lemon juice, cinnamon, and salt. Toss until berries are evenly coated. Spread mixture in prepared baking dish.
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 dry ingredients. Stir gently until just combined - batter will remain thick and slightly lumpy. Avoid overmixing.
05 - Drop rounded spoonfuls of batter over blueberry filling, covering surface while leaving small gaps for steam to escape and berries to bubble through.
06 - Bake for 40-45 minutes until topping turns golden brown and feels set when touched, and fruit filling bubbles actively around edges.
07 - Let cobbler rest for 15 minutes to allow filling to thicken. Serve warm with vanilla ice cream or whipped cream.