Preheat oven to 375°F.
Heat olive oil in a skillet. Add onion and sauté 2–3 minutes.
Add ground chicken, cumin, salt, and pepper. Cook until browned.
Stir in rice and entire jar of Butter Masala Sauce. Simmer 3–5 minutes.
Stuff each bell pepper with filling. Place upright in a baking dish.
Top with mozzarella (optional). Cover with foil and bake 25–30 minutes.
Garnish with cilantro and serve with lime wedges.