01 - Preheat oven to 375°F. Lightly grease a baking dish with olive oil or cooking spray.
02 - Slice the tops off the bell peppers and remove all seeds and membranes. Place the peppers upright in the prepared baking dish.
03 - In a large skillet, heat olive oil over medium heat. Sauté the finely chopped onion for 2–3 minutes until softened. Add minced garlic and cook for another 30 seconds until fragrant.
04 - Add ground chicken to the skillet. Cook, breaking it apart with a spoon, until no longer pink throughout, about 5–7 minutes.
05 - Stir in the diced tomato, chopped spinach, parsley, dill, dried oregano, ground cumin, paprika, salt, and pepper. Cook for 2–3 minutes until the spinach wilts. Mix in cooked rice or quinoa if using, then remove from heat.
06 - Allow the mixture to cool slightly, then gently fold in the crumbled feta cheese.
07 - Spoon the chicken mixture into each bell pepper, packing gently but not overstuffing.
08 - Pour chicken broth into the bottom of the baking dish to keep the peppers moist during baking. Cover the dish tightly with aluminum foil.
09 - Bake covered for 30 minutes. Remove the foil and bake an additional 10 minutes until the peppers are tender and the tops are lightly golden.
10 - Garnish with additional fresh herbs and crumbled feta if desired. Serve warm.