Cook the rice.
Cook ground beef and onion until done.
Meanwhile, slice peppers in half lengthwise; parboil peppers for 5 minutes and drain.
Once beef and onions are done, drain off the fat.
Add tomato sauce to the beef and onion mixture and simmer for 5 minutes.
When rice is done, combine it with the beef mixture.
Place peppers in a baking dish.
Fill peppers with the beef and rice mixture.
Pour tomato sauce AROUND the peppers (not over).
Cover the baking dish. Bake at 350°F for 35 minutes and then uncover and top with the shredded cheese.
Bake uncovered for about 5 minutes more to melt cheese.
