In a large skillet, heat oil and add ground beef. Cook, stirring to break up lumps, until no longer pink, about 5 minutes.
Add onion, garlic, ginger, curry, garam masala and cayenne pepper (if using). Continue to cook, stirring, until onion is soft, about 3 minutes.
Add sweet potato, tomatoes in juice and coconut milk. Bring to boil, cover, reduce heat to medium and simmer for 15 minutes.
Add peas and cook just to heat through. Serve over rice with chopped fresh cilantro and naan.