• Preheat the oven to 400°F. Generously spray a 9×13 glass⁵ or ceramic pan with baking spray.

Make the batter:

• In a 2-cup measuring glass or medium-sized bowl, mix together the cooled butter, buttermilk (or milk and vinegar), and vanilla until combined. In a separate medium bowl, whisk together the sugar, flour, baking powder, and salt. Add the wet mixture to the dry mixture, stirring until combined and no clumps are visible. Set aside.

Make the filling:

• In a large bowl, toss together all of the blueberries with the sugar, cornstarch (if using frozen berries), lemon zest, lemon juice, salt, and cinnamon.

Assemble:

• Spread blueberry mixture evenly into the prepared pan. Pour batter on top of the blueberries, carefully spreading across the top of the berries if needed (but don’t worry if it’s not all the way to the edges!). Sprinkle coarse sugar evenly over batter.
• Bake for 45 minutes, or until the top is golden brown and set, then use a toothpick to test in several places throughout for doneness. The golden brown crust on top can be deceiving. If the toothpick doesn’t come out clean, tent the pan with aluminum foil and place back in the oven for about 5-10 minutes, or until the tester comes out clean.
• Once the cobbler has been removed from the oven, let sit until just warm before serving, about 30 minutes.
• Serve fresh with vanilla ice cream or homemade whipped cream. Enjoy!