Whisk buttermilk, eggs, sugar and butter in large bowl until well blended. Combine cornmeal, flour, baking powder and salt in medium bowl; stir into buttermilk mixture. Let stand 5 minutes.
Lightly grease large cast iron skillet; heat over medium heat. Pour batter into skillet by ⅓ cupfuls. Cook 3 minutes or until tops of pancakes are bubbly and appear dry; turn and cook 2 minutes or until bottoms are golden. Serve with blueberries and maple syrup, if desired.