Preheat oven to 350°F. Grease a 9-inch square baking dish.
Whisk melted butter with sour cream in a large bowl.
Stir in both cans of corn and the green chiles.
Fold in cornbread mix, salt, pepper, garlic powder, and cumin until just combined.
Mix in 1 cup cheddar. Spread the batter evenly in the pan.
Bake 35 minutes. Sprinkle remaining cheese on top; bake 8–10 minutes more until set and golden.
Cool 10 minutes. Garnish with green onions and serve warm.