Vanilla or Pralines and Cream ice cream, for serving
Preheat your oven to 400ºF.
In a cast iron skillet, combine the blueberries, 1/2 cup of sugar, cornstarch, lemon zest, and lemon juice. Place the pan over medium heat and allow it to cook down until the berries burst and bubble and start to create a jammy sauce.
Meanwhile, prepare the cornbread dumpling topping by combining the flour and cornmeal with the remaining 1/4 cup of sugar. Add in the baking powder and kosher salt and mix well. Using your hands, cut in the butter until it resembles a crumbly mixture with bits of butter about the size of a pea. In a separate bowl, whisk together 1/2 cup of buttermilk with the egg and add it to the dry ingredients. Stir just until a nice doughy batter is formed, adding a little more buttermilk if needed.
When the blueberry mixture is all bubbly and thick, use two spoons to drop the cornbread dumpling mixture evenly across the top. Turn the heat down to low and cover the pan with either a lid or a piece of tinfoil. Allow this to cook on the stovetop for ten minutes without removing the lid then remove the lid and place the whole pan in the preheated oven for five to eight minutes just to brown the top a little.