In a large bowl, combine the cornmeal, flour, sugars, baking soda and salt. In another bowl, whisk the egg, buttermilk and oil; stir into dry ingredients just until moistened. Pour into a greased 9-in. round or square baking pan (pan will be full).
Bake at 425° until a toothpick inserted in the center comes out clean, 20-25 minutes. Cool on a wire rack for 5 minutes. Serve warm.