Preheat the oven to 375°F (190°C).
Lightly grease a 9x13-inch baking dish.
Prep the peppers: Slice off the tops, remove seeds and membranes, and trim the bottoms if needed so they stand upright. Place them cut-side up in the baking dish.
Par-cook the peppers (optional but recommended): Add 1/4 inch of water to the dish, cover tightly with foil, and bake for 10 minutes. Drain any water and set aside.
This helps the peppers soften evenly.
Make the filling: Heat olive oil in a large skillet over medium heat. Add the onion and cook 3–4 minutes until softened. Stir in the garlic and cook 30 seconds.
Add the ground turkey.
Cook, breaking it up with a spoon, until no longer pink, about 5–6 minutes. Sprinkle in chili powder, cumin, smoked paprika, oregano, salt, and pepper. Stir to coat.
Stir in tomato paste and cook 1 minute to deepen the flavor.
Add the diced tomatoes with green chiles (with their juices). Simmer 2–3 minutes until slightly thickened.
Fold in black beans, corn, and cooked rice. Taste and adjust seasoning with more salt or spices as needed.
Remove from heat and stir in half the cheese and the cilantro if using.
Stuff the peppers generously with the turkey mixture, mounding slightly. Top with the remaining cheese.
Bake uncovered for 18–22 minutes, until the peppers are tender and the cheese is melted and lightly browned. If you want extra color on top, broil for 1–2 minutes at the end.
Rest 5 minutes, then serve with lime wedges and a dollop of sour cream or Greek yogurt if you like.