Preheat oven to 400°F. Spray a 9x9-inch baking pan, standard loaf pan or a 12 cup muffin tin with nonstick baking spray. Place all dry ingredients in a medium mixing bowl and blend well. Add buttermilk, egg and vegetable oil. Stir until just moistened. Let batter rest 5 minutes to thicken. Pour into prepared pan and spread evenly. For muffins, fill cups 3/4 full. Baking times for 9-inch pans is 25-30 minutes; for muffins 15-20 minutes. Finished baked cornbread will be very light golden brown. Serve hot with butter.