Preheat your oven to 325º F.
Peel off the outer skin from your Vidalia onions. Using a spoon, hollow out the centers of the onions - leaving 2 layers of onion on the outer end. Reserve the onions for a later use or sauté them with the ground beef in the chili. Slice off the very bottom of the root end to make a flat surface so the onion can stand up.
In a pot, cook the ground chuck & reserved Vidalia onion (if using). Add the chili seasoning pack, kidney beans, & diced tomatoes. Stir well & cook until warmed. Turn off the heat.
Season the hollowed out insides of the onions with salt & pepper. Press about 2 tablespoons of shredded cheddar cheese into the very bottoms of the hollowed onions. Spoon chili into the onions to the top. Cover with foil, bake for 90 minutes.
Remove from the oven, top each onion with a heap of shredded cheddar cheese. Bake uncovered for about 5 more minutes or until the cheese is melted.