Slice off one side of each poblano to create a boat like vessel. Chop the removed pepper pieces and add to the other peppers. Place the pepper boats in a baking pan that has been coated with cooking spray and set aside.
If you don't have cooked rice, cook 1/2 cup of brown rice in 1-1/2 cups of vegetable stock or water that is seasoned with half of each the cumin and chili powder. This should take 30 - 40 minutes. You can do this earlier in the day or even the night before.
In a large fry pan heat the olive oil. Add the chopped onions, peppers, and garlic, tossing to coat everything. Cook over medium heat until everything begins to soften.
Add the remaining cumin and chili powder and let them cook and get fragrant for a couple of minutes. Stir in the rice and toss until well combined with the vegetables. Cook a couple of minutes more.
Add the chili or tomato sauce, stirring it in well. Allow to cook a few more minutes. If the mixture seems dry add some of the vegetable stock as the mixture cooks. Stir in the drained beans and toss to combine.
Divide the filling between the pepper boats. They will be filled to overflowing which is perfectly fine. Cover loosely with foil and bake at 350 degrees for 20 - 25 minutes. The boats should be soft and the filling hot.
Remove the foil and sprinkle some of the shredded cheese on top of each pepper. Broil for 3 minutes or so until the cheese is melted and beginning to brown.
Remove from the oven and allow to rest for 5 minutes before serving. Pass your hot sauce of choice at the table.