Preheat the oven to 350 degrees F.

In a large pot of boiling water, parboil the peppers until just tender, 2 to 3 minutes. Remove with a slotted spoon and dry on paper towels.

In a large saute pan or skillet,  brown beef, garlic, parsley, salt, black pepper, and pepper flakes. Cook until the meat is browned, stirring with a heavy wooden spoon to break up the lumps, about 6 minutes. Add the cooked rice, cheese and tomato sauce and stir well. Remove from the heat and adjust the seasoning, to taste.

Pour remaining tomato sauce (or water) into a baking dish to just cover the bottom, about 1/8-inch deep. Stuff the bell peppers with the rice mixture and place in the baking dish. Bake until the peppers are very tender and the filling is heated through, 25 to 30 minutes.  You can put more cheese on top for last 10-15 minutes if desired.

Remove from the oven and let rest for 10 minutes before serving.

From Food Network, tweaked by me.