2⁄3 cup vegetable oil, plus more for greasing
1 cup sour cream
2 large eggs, lightly beaten
1 medium yellow onion, grated
1 (16-oz.) can creamed corn
1 1⁄2 cups yellow cornmeal
2 tsp. baking powder
1 tsp. kosher salt
1 cup (about 5 oz.) grated cheddar cheese
Heat the oven to 350° and grease a 9-inch round cast-iron skillet. In a medium bowl, whisk the oil with the sour cream, eggs, onion, and corn until evenly combined. In another bowl, whisk the cornmeal with the baking powder and salt. Add the dry ingredients to the wet ingredients and stir until they form a slightly lumpy batter.
Scrape half the batter into the prepared skillet, sprinkle with 3⁄4 cup cheese, and spread the remaining batter on top. Sprinkle the top with the remaining cheese and bake until golden brown and a toothpick inserted in the center comes out clean, about 45 minutes. Transfer the skillet to a rack and let the cornbread cool for 20 minutes before serving.