Before making this recipe, make sure your cast iron skillet is well-seasoned. Preheat your oven to 400 degrees.
Coat the interior of your cast iron skillet with olive oil, wiping off any excess with a paper towel. You just want a thin layer of olive oil.
Begin by melting your butter in a medium, microwave-safe mixing bowl. Once it's melted, let it cool slightly so that it's not super hot (you don't want to curdle the eggs when you add them). Once it's cooled a bit, whisk in the room-temperature buttermilk and olive oil.
Then, add in the egg and egg yolk and whisk until that mixture is evenly combined. Set aside.
In another large mixing bowl, combine all of the dry ingredients and whisk together until evenly combined.
Pour the wet ingredients into the bowl with the dry ingredients, and mix together until totally combined.
Pour the batter into the oiled cast iron skillet, and use a spatula and smooth out the top. The texture at this point should more of a paste, not a liquid. Let the batter rest in the skillet at room temperature for 5 minutes.
Then, bake your cornbread in the oven at 400 degrees F for 20-25 minutes, or until a toothpick comes out with a few moist crumbs on it, when poked into the cornbread about 2 inches from the edge of the skillet.
While the cornbread is baking, make the spicy honey butter. Melt the butter and stir in the Piment d'Espelette and the honey.
When the cornbread is done, and while it's still hot from the oven, brush the spicy butter over the top.
Let the cornbread cool before cutting into slices. The best way to do this is to tilt the skillet upside down and remove the entire cornbread. From there, you can place it on a plate and cut it into slices.
Enjoy!