Preheat your oven to 350°F (175°C) to ensure even baking.
In a large mixing bowl, combine the fresh blueberries, lemon juice, lemon zest, light brown sugar, granulated sugar, cinnamon (if using), cornstarch, vanilla extract, and salt. Gently toss until blueberries are well coated.
In another bowl, whisk together the flour, baking powder, and salt. In a separate bowl, mix the melted butter, granulated sugar, and vanilla extract until well combined. Gradually add the dry ingredients to the wet mixture and stir until just combined.
Spread the blueberry filling evenly in the bottom of your baking dish. Drop spoonfuls of the cobbler topping over the blueberries.
Sprinkle turbinado sugar and cinnamon over the top and bake for 35-40 minutes, until the topping is golden brown and the blueberries are bubbling.
Allow the cobbler to cool for at least 15 minutes before serving. Serve warm, ideally with vanilla ice cream or whipped cream.