1/3 to 1/2cupgranulated sugar(depending on how sweet you like your cornbread)
2/3cupbuttermilk(preferably, whole, but low-fat can be substituted)
8tablespoonsunsalted butter, divided
Place an 8- to 9-inch cast iron skillet in a cold oven (rack in middle position) and preheat to 400 degrees F.
In a large bowl, whisk together cornmeal, flour, sugar, baking soda, baking powder, and salt. Set aside.
Melt and cool 7 tablespoons of butter (cooling is important). In a bowl, whisk together eggs, buttermilk, and sour cream. Whisk in melted butter. The mixture will look a little curdled--this is the butter chilling into tiny clumps and is the desired result.
Stir the wet ingredients into the dry ingredients until just combined. For tender cornbread, don't overmix.
Remove the heated skillet from the oven and immediately add the remaining 1 tablespoon of butter. Use a heat-safe basting brush to swirl it around the pan's bottom and sides. When fully melted and foaming subsides, pour the cornbread batter into the skillet, spreading it into an even layer. It will immediately start to set on the edges.
Bake for 20-25 minutes, until golden brown and a skewer inserted into the center comes out with just a few moist crumbs attached.
Cool cornbread for about 15 minutes, slice into wedges, and serve warm with whipped butter, honey butter, or maple butter.
For storage instructions see the Make Ahead section above.