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, sugar, cornstarch, lemon juice, cinnamon, and salt. Toss until berries are evenly coated. Spread mixture in the 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 the flour mixture. Stir gently until just combined—the batter will be thick. Avoid overmixing.
05 - Drop spoonfuls of batter evenly over the blueberries, covering most of the surface. Leave small gaps to allow steam to escape and fruit to bubble through.
06 - Bake for 40 to 45 minutes until topping is golden brown and cooked through, and berry filling is bubbling around the edges.
07 - Let cobbler cool for at least 15 minutes before serving. Serve warm with vanilla ice cream or whipped cream if desired.