Preheat oven to 350 degrees. Cut the tops off peppers and scoop out insides. Parboil cups for approx. 5 minutes (dice up the tops and freeze for another day). In saucepan, bring rice and broth to a boil, turn down and simmer covered for about 15 minutes. Brown hamburger and onions in a deep skillet. Drain off grease.
Mix hamburger, onions, rice, garlic powder, tomatoes and worcestshire sauce. Turn over very low for about 10 minutes. Stir in 1 cup of shredded cheese. Spoon into pepper cups in a casserole dish. (I usually spoon remaining meat mix on cabbage leaves and roll them up, but that's another recipe LOL). Cover, bake for 40 minutes, sprinkle remaining cheese on top and return to oven uncovered for 5 more minutes.