Preheat the oven to 350 degrees Fahrenheit and spray a 9×13 baking dish with nonstick spray.
Cook 1 ½ pounds of lean ground beef in a large skillet over medium-high heat until no longer pink. Add the diced ½ cup of onion and cook until tender.
Add 1 (15 ounces) can of corn, 1 (15 ounces) can of chili beans, 1 (10 ounces) can of Rotel tomatoes, 1 teaspoon of salt, ½ teaspoon of black pepper, ½ teaspoon of garlic powder, 2 teaspoons of chili powder, and 2 teaspoons of cumin. Stir to combine.
Pour the beef mixture into the prepared pan, then top it with 2 cups of Colby-Jack cheese.
Combine 2 (8.5 ounce) boxes of Jiffy corn muffin mix, 1 (15 ounces) can of creamed corn, and ½ cup of sour cream in a medium bowl and mix until you have a thick batter.
Spoon the mixture evenly over the casserole.
Bake for 35 to 40 minutes or until the cornbread is golden brown.