Adjust oven rack to center position and preheat oven to 425°F. Heat butter in a 12-inch cast iron or stainless steel skillet over medium heat until melted. Continue to cook and extra water from the butter, swirling pan gently until nutty-smelling and toasty brown. Be careful not to burn! Transfer to a heatproof cup or bowl and reserve for cornbread.
Return pan to high heat. Add beef and cook, stirring and browning with a wooden spoon, about 8 minutes. Add onion and garlic and cook, stirring frequently, until softened and fragrant, about 4 minutes. Add chili powder, cayenne (if using), cumin, and coriander. Stir until fragrant, about 30 seconds.
Add corn, black beans, tomatoes, and chicken stock. Bring to a simmer, then stir in cheese. Reduce heat to low and cook, stirring occasionally, until thickened into a rich stew-like consistency, about 5 minutes. Remove from heat and stir in scallions and cilantro. Season to taste with salt and pepper.
For the Cornbread Crust:
Combine cornmeal, flour, sugar, 1 teaspoon kosher salt, baking powder, and baking soda in a large bowl. Combine eggs, sour cream, and buttermilk in a second bowl and whisk until homogenous. Whisking constantly, slowly drizzle in reserved browned butter. Whisk wet ingredients into dry ingredients until smooth.
Using a large spoon, place small dollops of the cornbread batter mixture on top of the beef filling, then use the back of the spoon to spread it into an even layer. Transfer the skillet to the oven and bake until pale golden brown and a skewer inserted into the cornbread comes out clean, about 20 minutes.
Let cool 15 minutes, then serve with sour cream, scallions and your favorite hot sauce.