Preheat and prep the peppers: Heat the oven to 375°F (190°C). Slice the tops off the peppers, remove seeds and membranes, and trim the bottoms if needed so they stand upright. Brush the insides with a little olive oil and a pinch of salt.

Par-bake the peppers: Place the peppers upright in a baking dish. Add a splash of water to the dish, cover with foil, and bake for 12–15 minutes until slightly softened. This helps them cook evenly later.

Cook the quinoa: Rinse the quinoa under cold water. In a saucepan, combine quinoa and broth with a pinch of salt. Bring to a boil, reduce heat, cover, and simmer for 15 minutes. Turn off heat and let steam for 5 minutes, then fluff with a fork.

Sauté aromatics: In a large skillet, warm 1 tablespoon olive oil over medium heat. Add onion and cook 3–4 minutes until translucent. Stir in garlic and cook 30 seconds until fragrant.

Brown the beef: Add ground beef to the skillet, season with salt and pepper, and cook, breaking it up, until browned, about 6–8 minutes. Drain excess fat if needed.

Season and build flavor: Stir in tomato paste, cumin, smoked paprika, oregano, and red pepper flakes. Cook 1 minute to toast the spices. Add drained diced tomatoes and simmer 2–3 minutes.

Combine with quinoa: Fold the cooked quinoa into the beef mixture. Taste and adjust seasoning with more salt and pepper as needed. The filling should be well-seasoned and slightly saucy.

Stuff and top with cheese: Spoon the filling into the par-baked peppers, packing it gently. Sprinkle cheese over each pepper.

Bake until melty: Return the peppers to the oven and bake uncovered for 12–15 minutes, until the cheese is melted and the peppers are tender.

Finish and serve: Let cool for a few minutes. Garnish with chopped herbs and a squeeze of lemon or lime if you like. Serve warm.