01 - Preheat the oven to 375°F.
02 - Slice off the tops of the bell peppers, remove seeds and membranes. Using a paring knife, carve jack-o’-lantern faces into the sides of each pepper.
03 - Place prepared bell peppers upright in a baking dish.
04 - Heat olive oil in a large skillet over medium heat. Add finely diced onion and cook until softened, about 5 minutes. Stir in minced garlic and cook for 1 minute.
05 - Add cooked brown rice, black beans, corn kernels, diced tomatoes, ground cumin, smoked paprika, chili powder, salt, and ground black pepper. Cook for 3 to 4 minutes, stirring occasionally until well combined.
06 - Remove skillet from heat. Mix in shredded cheddar cheese and chopped cilantro if using.
07 - Fill each bell pepper with the black bean mixture, pressing gently to compact. Top with additional cheese if desired.
08 - Replace the tops on the peppers. Add a splash of water to the baking dish. Cover with foil and bake for 30 minutes.
09 - Remove foil and bake an additional 10 minutes, until the peppers are tender and cheese is melted.
10 - Serve the stuffed peppers warm.