Prep the peppers. Preheat your oven to 400°F (200°C).
Slice peppers in half lengthwise, remove seeds and membranes, and place cut-side up in a baking dish. Drizzle with olive oil and a pinch of salt. Bake for 12–15 minutes to soften while you make the filling.
Sauté the aromatics. Warm a tablespoon of olive oil in a large skillet over medium heat.
Add diced onion and cook until softened, about 3–4 minutes. Stir in garlic and cook 30 seconds until fragrant.
Brown the protein. Add ground turkey and break it up with a spoon. Cook until no longer pink, about 5–7 minutes.
Season with taco seasoning, a pinch of salt, and pepper.
Build the sauce. Stir in tomato paste to coat the meat. Add broth and simmer 2 minutes to create a saucy base that binds the filling.
Add the mix-ins. Fold in black beans, corn, and cooked brown rice or quinoa. Warm through for 2–3 minutes.
Taste and adjust seasoning with more taco spice, salt, or a squeeze of lime.
Stuff the peppers. Spoon the filling into the pre-baked pepper halves, mounding slightly. Sprinkle with shredded cheese.
Bake to finish. Return to the oven for 10–12 minutes, until the peppers are tender and the cheese is melted and bubbly. If you like browned tops, broil for 1–2 minutes.
Garnish and serve. Top with chopped cilantro or green onions.
Add a squeeze of lime and any extras like Greek yogurt, avocado, or salsa. Serve hot.