Heat the oven to 400 degrees. While the oven is heating up, place your 10" cast iron skillet in the oven to heat up.
In a medium-sized bowl, add the cornbread mix, 1/2 cup of cheddar cheese, milk, egg, and canned corn. Stir until well combined.
When the oven is heated, carefully take out the skillet, pour in the cornbread mixture, and bake for 15 minutes.
Dice the onion and pepper and add to a large skillet with the butter. Cook until softened.
Add the ground beef to the skillet and cook through. Drain the fat. (I usually use 90/10 percent fat ground beef and there usually isn't any fat to drain off).
Add all but 1/2 cup of the sloppy joe sauce to the pan with the meat to warm.
Remove the cornbread from the oven and use a fork to prick holes over the cornbread. Pour the remaining 1/2 cup of the sloppy joe sauce over the cornbread.
Spoon the meat and sauce over the baked cornbread and top with the remaining cheese. Return to the oven for 15 minutes.