Blanch peppers (any color) in boiling water - wait until water is boiling, cut off tops and remove insides, submerge in boiling water for about 8 minutes or until they have just softened. Remove, set aside.
Cook your rice while you're doing that and brown your ground beef. When rice and ground beef are cooked mix them together with your spaghetti sauce, salt, and cheese.
Put blanced peppers in a muffin tin so they don't fall over and fill them with your rice mixture.
Put in preheated oven at 350 degrees for maybe 15-20 minutes just to meld all the flavors together. Can add more cheese to the top of each one for last 5 minutes if desired too.