Preheat the oven to 375°F. Cut the tops off the peppers and remove the seeds and ribs. Stand the peppers in a baking dish.
In a bowl, stir together the rice, beans, tomatoes, chili powder, cumin, garlic powder, salt and half of the cheese.
Spoon the filling into the peppers, mounding it on top.
Pour ¼ cup of water into the bottom of the dish and cover tightly with foil.
Bake for 25 minutes. Uncover, sprinkle with the remaining cheese and bake for 10–15 minutes more, until the peppers are tender and the cheese is melted.