Preheat your oven to 350°F (175°C).
In a skillet, brown the ground beef over medium heat until fully cooked.
Drain excess fat from the beef and season with salt and pepper.
Add kidney beans, diced tomatoes, and corn to the skillet. Stir to combine.
In a mixing bowl, combine cornbread mix, milk, and egg until smooth.
Spread the beef mixture evenly in a greased casserole dish.
Pour the cornbread mixture over the beef layer.
Bake in the preheated oven for 25 minutes.
Remove the casserole from the oven and spread sour cream over the top.
Sprinkle cheddar cheese on top and bake for an additional 15 minutes, or until cheese is melted and bubbly.