Place a 10” cast-iron pan in oven; preheat oven to 350°F.
Using a large mixing bowl, add the dry ingredients (cornmeal, flour, baking powder, sugar, garlic powder and salt); whisk together until well combined.
Add 1 cup of shredded cheese, green chilies, white onions, green onions, buttermilk, 3 Tbsp of melted butter, egg and corn; stir until mixture is just combined.
Remove hot skillet from oven and add remaining 1 Tbsp of melted butter; brush butter around bottom and sides of skillet.
Pour batter into skillet. Sprinkle remaining ½ cup of shredded cheese on top.
Bake at 350°F for 40-45 minutes, or until top of cornbread is golden brown in color and a toothpick inserted into the center of the cornbread comes out mostly clean.
Remove skillet from oven and let cornbread cool slightly before serving. (Note: Serving the cornbread in the skillet helps keep it warm – just make sure to place skillet on a hot pad before placing it on the table!)
Notes
If you don't have a 10" cast iron skillet, this cornbread can be baked in a 9" square baking dish.