Preheat oven to 375 degrees F.
Grease a 9 or10-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 the egg and buttermilk together. Stir buttermilk mixture into dry ingredients. Stir in melted butter and mix gently. Add corn, 2/3 cup cheddar cheese and minced jalapenos. Pour batter into prepared pan and top with remaining cheddar cheese. Bake for 20 to 25 minutes or until an inserted knife comes out clean. Let cool for 5 minutes and invert onto a cooling rack.