Preheat oven to 375 degrees. Grease a 9 - 10-inch cast iron skillet or a 9 inch square pan.
In a large bowl combine cornmeal, flour, sugar, baking powder, baking soda and salt. In a liquid 2 cup measure or a small bowl, mix together the egg and the buttermilk. Stir buttermilk mixture into dry ingredients. Add corn, 2/3 cup cheddar cheese and minced jalapenos. Stir in melted butter and mix gently. Pour batter into prepared pan and top with remaining cheddar cheese. Bake for 20-25 minutes or until broken down and an inserted knife comes out clean. Let cool for 5 minutes and remove from pan to a cooling rack