1. In a large bowl mix together the cornmeal, flour, salt, and baking powder. In a separate bowl, mix together the eggs, margarine, and buttermilk. Add to the dry ingredients and stir until well blended.
2. Heat a dry 12 inch cast iron skillet over high heat for 2 minutes. Add corn oil to skillet, swirl oil around to coat bottom and sides. Leave remaining oil in pan. Return to high heat for 1 minute. Pour the cornbread batter into the skillet and cook on high heat until bubbles start to form in the center. Remove from stove.
3. Bake in a preheated 400 degree F (200 degree C) oven for 40 to 50 minutes, or until a knife inserted into the center comes out clean. Serve warm.