Preheat the oven to 375°F.
In a large skillet over medium heat, cook the ground beef or turkey until browned, about 5-7 minutes. Drain excess fat if necessary.
Add the cooked rice, black beans, diced tomatoes, chili powder, cumin, garlic powder, salt, and pepper to the skillet. Stir to combine and cook for another 5 minutes until heated through.
While the filling is cooking, slice the tops off the bell peppers and remove the seeds and membranes.
Place the hollowed peppers upright in a baking dish.
Spoon the filling mixture evenly into each pepper, packing it down gently.
Top each stuffed pepper with shredded cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, until the peppers are tender and the cheese is bubbly and golden.
Let the peppers cool for a few minutes before serving. Garnish with fresh cilantro or parsley if desired.