I usually do the peppers first.  Fry them with a little oil in a fry pan with cover in batches so that all peppers are touching pan. When done put them aside to cool.

Cook rice.

Cook the onion in fry pan and then add ground beef when onion is almost done.  I then mix in the rice with the onions and beef.  Next add tomato sauce, Worcestershire sauce, a little ketchup, chili powder, and cumin.  I add enough sauce to get the consistency I want.

Layer half the peppers in bottom of Pyrex dish.  Add the beef and rice mixture.  Put the other half of the peppers on top.  Add a little more sauce over the peppers.  I cover it with plastic wrap and cook in microwave for about 20 minutes.  Remove the plastic wrap carefully.  Add cheese to top and microwave more to melt cheese.  Let sit for about 20 minutes so its not too runny when you serve it.