Preheat over to 350 degrees. Spray an 8-inch square or 9 inch round baking pan with a light coating of vegetable oil. Set aside.
In a large bowl, beat the brown sugar, egg, egg white, canola oil, buttermilk and sweet potatoes until frothy. Sift together the cornmeal, flour, salt and baking powder into the mixing bowl. Gently fold the ingredients until just mixed. Pour the batter into the oiled pan and bake for 20 - 25 minutes, until a knife inserted into the center comes out clean. Serve hot or at room temperature.