Preheat the oven to 400 degrees F. Pour the oil into a 9-inch cast-iron skillet or round pan, and preheat in the oven.
In a small bowl, combine the cornmeal, sugar, salt, and baking soda. In a large bowl, combine the starter, buttermilk, eggs and butter, and blend well. Add the dry ingredients, and stir until combined without overmixing. Remove the hot skillet from the oven. Pour the batter into the hot skillet and bake until golden, 25 to 30 minutes.