1. Heat oven to 400 degrees F. Coat 12 jumbo-size muffin-pan cups with nonstick cooking spray.
2. Mix flour, cornmeal, 2/3 cup sugar, baking powder, baking soda and salt in large bowl.
3. Beat egg whites on high speed in small bowl until frothy. Gradually beat in the remaining 1/3 cup sugar until stiff, moist peaks form. Set aside.
4. Mix egg yolks, buttermilk and 2 tablespoons melted butter in medium-size bowl. Stir buttermilk mixture into flour mixture just until evenly moistened. Gently fold beaten whites into cornmeal mixture until no white streaks remain. Spoon rounded 1/3 cup batter into each prepared cup.
5. Gently brush tops with remaining melted butter. Sprinkle with remaining 1-1/2 teaspoons sugar, dividing evenly.
6. Bake in 400 degree F oven for 20 minutes or until wooden pick inserted in centers comes out clean. Remove muffins from pan to rack; let cool. Makes 12 muffins.