Preheat your waffle iron. In a medium mixing bowl, stir together the flour, cornmeal, sugar, baking powder, baking soda, and salt. In a smaller bowl, whisk together the eggs, buttermilk, vanilla and melted butter. Pour the buttermilk mixture into the dry ingredients and stir together thoroughly to combine and form a thick batter (there may be lumps, but that’s ok).
Grease the waffle iron as needed with butter. Using a 1 cup measuring cup, scoop the batter into the center of the preheated waffle iron. Sprinkle a generous handful (about 1/4-1/3 cup) of blueberries on top of the batter. Close the waffle iron and cook until golden brown and crisp on the exterior, about 5 minutes. Transfer the waffle to a plate and serve immediately with pure maple syrup and butter. Repeat with remaining batter and blueberries.
Note: Waffles get soggy as they sit. If unable to serve immediately, keep waffles hot on sheet pan lined with a wire rack in a 200 degree oven.