Preheat oven to 400 degrees F and place rack at center.
In a large measuring cup, beat together the eggs, milk, and oil. Set aside.
In a medium bowl, mix together the cornmeal, flour, sugar, salt, pepper, and baking powder.
Pour the milk mixture into the bowl with the cornmeal mixture and stir until just combined. Stir in onion.
Place a 9-inch cast iron skillet on a burner and heat over medium flame for two minutes. Drizzle in the extra tablespoon of oil and let heat a minute. Swirl the pan or use a brush to make sure the oil covers the bottom and even up the sides a bit. Sprinkle the extra tablespoon of cornmeal evenly over the oiled pan. Heat until cornmeal shows just a little color—pale golden.
Pour the mixed cornbread batter into the hot pan, grate some pepper on top (4-6 grates) and give it two minutes or so to heat. A small bubble or two may appear at edges, and then it’s time to put the pan in the oven. Bake 15-20 minutes until quite brown around the edges and lightly golden on top. Remove from the oven, cut and serve hot, warm, at room temperature, or cold with butter. (Don’t forget grilling the leftovers, too.)