1. Preheat the oven to 450 degrees F (230 degrees C). Lightly grease twelve muffin cups (if you're not using a non-stick pan), or line them.
2. Mix cornmeal, all-purpose flour, baking powder, baking soda, salt and sugar together in a large bowl. Beat together buttermilk, eggs and vegetable oil in another bowl. Pour wet ingredients into dry and mix well. Pour batter into muffin cups. (They will be full to the top.)
3. Bake 15-18 minutes, or until muffin tops turn slightly brown and a toothpick comes out clean.