Prep the peppers: Preheat your oven to 400°F (200°C). Slice bell peppers in half lengthwise and remove seeds and membranes.
Place them cut-side up in a baking dish. Lightly season with a pinch of salt.
Soften the peppers: Add 1/4 cup water to the baking dish and cover tightly with foil. Bake for 12–15 minutes to soften slightly.
Drain any excess liquid and set peppers aside.
Sauté aromatics: While peppers bake, heat olive oil in a large skillet over medium heat. Add onion and cook 3–4 minutes until softened. Stir in garlic and cook 30 seconds until fragrant.
Brown the turkey: Add ground turkey, salt, and pepper.
Cook 5–6 minutes, breaking it up with a spoon, until no longer pink.
Season the filling: Stir in chili powder, cumin, smoked paprika, oregano, and red pepper flakes if using. Cook 1 minute to bloom the spices.
Add mix-ins: Stir in diced tomatoes, corn, black beans (if using), and broth. Simmer 3–4 minutes, letting flavors meld and excess liquid reduce slightly.
Fold in grains: Add cooked brown rice or cauliflower rice.
Mix well. Taste and adjust salt, pepper, or spices as needed. Turn off the heat and stir in half of the cheese.
Stuff the peppers: Spoon the turkey mixture into each pepper half, packing it in to fill them generously.
Bake: Top with the remaining cheese.
Cover with foil and bake 10 minutes. Remove foil and bake another 8–10 minutes, until cheese is melted and bubbly and peppers are tender.
Finish and serve: Garnish with cilantro and any toppings you like. Serve with lime wedges for a bright squeeze over the top.