Preheat oven to 450 degrees F (232 degrees C) with racks in the lower-middle and middle positions. Place a 10-inch oven-safe skillet on the middle rack for 10 minutes to preheat.

Spread cornmeal on a baking sheet and bake on the lower-middle rack for about 5 minutes, until fragrant and the color begins to deepen. Transfer the hot cornmeal to a large bowl and whisk in buttermilk; set aside.

Add canola oil to the hot skillet and continue to bake until the oil is just smoking, about 5 minutes. Remove skillet from the oven and add unsalted butter, carefully swirling the pan until the butter is melted.

Pour all but 1 tablespoon of the oil/butter mixture into the cornmeal mixture, leaving the remaining oil/butter in the pan.

Whisk baking powder, baking soda, salt, and eggs into the cornmeal mixture.

Pour the cornmeal mixture into the hot skillet and bake until the top begins to crack and the sides are golden brown, about 12 to 16 minutes.

Let the corn bread cool in the pan for 5 minutes, then turn it out onto a wire rack to cool slightly before serving.