• 1 1/2 cups all-purpose flour
• 3/4 cup cornmeal
• 1/2 cup granulated sugar
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon ground cinnamon
• 1/4 teaspoon salt
• 2 teaspoons finely grated orange zest
• 1 1/4 cups low-fat buttermilk, plus about 2 tablespoons for tops
• 2 large eggs, separated
• 2 tablespoons unsalted butter, melted
• 1 1/2 cups blueberries (about 1/2 pound), picked over and rinsed

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.