Cut off tops of peppers, and remove seeds. If needed, cut a thin slice off the bottom (without going all the way through) so the peppers stand. Place peppers in a dish and microwave on high for 5 minutes.
Optional step: dice edible portion of the pepper tops (discard insides and stems of peppers) to be added with the beef.
Meanwhile, add beef and onion (and diced peppers if using) to a medium skillet. Cook until browned, breaking up meat with meat chopper or a wooden spoon, about 5 minutes. Add 1 cup tomato sauce, 1 cup of water, and Italian dressing mix. Bring to a boil.
Remove from heat. Add rice, stir, cover, and allow to rest for 5 minutes.
Mix together remaining tomato sauce and ¼ cup water in bottom of a 3 quart or 9 inch casserole dish.
Fill peppers with rice mixture and add to baking dish. Top peppers with cheese.
Cover and bake for 30 to 35 minutes, until peppers are tender. Broil for 1-2 minutes to brown cheese if desired.
Top peppers with sauce and serve!
*Rice filling will fill 4-6 peppers depending on the size of the peppers and how full you fill them.Tip: if covering with foil, spray to avoid sticking