Preheat oven to 400°F (200°C). In a 10-inch oven-safe skillet over medium-high heat, cook the beef and onion, breaking up meat, until beef is no longer pink, 6-8 minutes. Stir in garlic and cook 30 seconds. Drain excess fat.

Stir chili powder, cumin, smoked paprika, and salt into the beef. Cook 30 seconds. Add enchilada sauce, tomatoes with juices, beans, and corn. Simmer on low for 10 minutes, stirring occasionally.

In a bowl, whisk masa harina, flour, sugar, baking powder, and salt. In another bowl, whisk buttermilk, egg, and melted butter. Stir wet into dry until just combined.

Remove skillet from heat. Spread batter over the filling, top with cheese, and bake 25-30 minutes until golden and a toothpick comes out clean.

Let rest 5 minutes, then slice and serve.