Preheat your oven to 375°F (190°C).
Slice the tops off the bell peppers and remove the seeds and membranes. Place them upright in a baking dish.
In a mixing bowl, combine the black beans, corn, cooked rice, salsa, chili powder, cumin, and salt. Mix well until all ingredients are evenly incorporated.
Spoon the bean mixture into the hollowed bell peppers, pressing down gently to pack it in.
If using shredded cheese, sprinkle it on top of each stuffed pepper.
Pour a little water in the bottom of the baking dish to help steam the peppers during cooking, cover the dish with aluminum foil.
Bake the stuffed peppers in the preheated oven for 25 minutes.
After 25 minutes, remove the foil and bake for an additional 5 minutes or until the peppers are tender and the cheese is melted and bubbly.
Remove from the oven and let cool slightly before serving. Garnish with fresh cilantro if desired.