Preheat the oven to 325 degrees F.

Butter a 2-quart baking dish.

In a large bowl, combine the blueberries, sugar, cornstarch, cinnamon, salt, and lemon zest and juice. Stir until the cornstarch has formed something of a slurry with the lemon juice. Scrape the fruit mixture into the buttered dish.

In the same bowl, combine the flour, cornmeal, sugar, baking powder, and salt. Whisk to combine. Add the butter and use a pastry blender to work it into the dry ingredients.

Add the milk and stir just enough to incorporate.

Spoon the cobbler topping over the blueberries, doing your best to make a fairly even layer.

Sprinkle the coarse sugar over the top of the dough.

Set the baking dish on top of a rimmed baking sheet and slide it into the oven.

Bake at 325 degrees F for 25 to 30 minutes, until the fruit looks thick and jammy.

Then, turn the heat up to 375 degrees F and bake for an additional 10 to 15 minutes. This gives the cobbler top a chance to brown a little more deeply.

Remove the cobbler from the oven and let it cool for at least 30 minutes before serving.