Preheat oven to 400 degrees, with rack in center. Lightly coat a standard muffin tin with cooking spray. In a medium bowl, whisk together flour, cornmeal, granulated sugar, baking powder, baking soda, cinnamon, salt, and orange zest, if using.
In a small bowl, whisk together buttermilk, egg yolks, and butter. Stir buttermilk mixture into flour mixture until just blended. In a mixing bowl, whisk the egg whites until just stiff. Gently fold whites and blueberries into the batter until just combined.
Spoon batter into prepared muffin tin, filling each cup three-quarters full. Bake 12 minutes. Remove from oven; gently brush tops with buttermilk, and sprinkle with sanding sugar, if desired. Continue baking until tops are golden and a cake tester inserted in a muffin center comes out clean, 6 to 8 minutes more. Let muffins cool slightly, about 10 minutes, before turning out of tin.
Recipe also appeared in Annual Recipes 2004