Preheat your oven to 375°F (190°C). Lightly oil a 9x13 baking dish with cooking spray or a drizzle of olive oil.
Prep the peppers. Cut the bell peppers in half lengthwise and remove the seeds and membranes. Brush the insides and outsides with olive oil and season with a pinch of salt and pepper. Place them cut-side up in the baking dish.
Par-bake the peppers. Place the peppers in the preheated oven for about 10-15 minutes while you prepare the filling. This partial pre-cooking ensures they'll be perfectly tender by the time the filling is hot.
Start the filling. While the peppers are pre-baking, heat 1 tablespoon olive oil in a large skillet over medium heat. Add the diced onion and cook until softened, about 3-4 minutes.
Add the turkey. Increase heat to medium-high and add the ground turkey to the skillet. Break it apart with a spoon as it cooks until no longer pink, about 5-7 minutes.
Bring on the flavor. Add the minced garlic and cook for 30 seconds until fragrant. Then add chili powder, cumin, oregano, smoked paprika, cayenne (if using), salt, and pepper. Stir to coat the meat evenly with the spices.
Add the mix-ins. Stir in the black beans, corn, diced tomatoes, and salsa. Simmer for about 5 minutes until some of the liquid has evaporated and the flavors have melded.
Finish the filling. Remove from heat and stir in the cooked rice or quinoa, fresh cilantro, and lime juice. Taste and adjust seasonings if needed.
Stuff the peppers. Remove the par-baked peppers from the oven. Spoon the filling into each pepper half, mounding it slightly (don't be shy—really fill them up!).
Top with cheese. Sprinkle the stuffed peppers with shredded cheese, dividing it evenly among all the pepper halves.
Bake to perfection. Return the stuffed peppers to the oven and bake for 15-20 minutes until the peppers are tender and the cheese is melted and bubbly.
Garnish and serve. Let cool for 5 minutes, then top with your choice of garnishes. Serve with lime wedges for squeezing over the top.