Preheat your oven to 375°F (190°C).
Carefully slice the poblano peppers in half lengthwise and remove the seeds.
In a bowl, mix the cooked rice, black beans, corn, diced tomatoes, cheese, cumin, chili powder, salt, and pepper.
Stuff each halved poblano with the filling mixture.
Place the stuffed peppers in a baking dish.
Cover the dish with aluminum foil.
Bake in the preheated oven for 20 minutes.
Remove the foil and bake for an additional 10 minutes until the cheese is bubbly.
Remove from the oven and let cool slightly.
Garnish with fresh cilantro before serving.