Prepare the ingredients as instructed above.
Cook rice: Rinse basmati rice thoroughly. Cook according to package directions. Fluff with a fork and season with salt and pepper to taste.
Make masala paste: In a small bowl, mix onion, garlic, ginger, cinnamon, chili powder, turmeric, cumin, lemon juice, and cayenne (if using).
Marinate chicken: In a separate bowl, combine chicken with Greek yogurt and half of the masala paste. Mix well, cover, and refrigerate.
Cook chicken: Heat olive oil in a nonstick pan over medium-high heat. Brown marinated chicken pieces on all sides, then remove and set aside.
Make sauce: In the same pan, add remaining masala paste and cook for 1 minute. Add tomato paste and browned chicken. Simmer for 10 minutes, until chicken reaches 160°F (71°C).
Finish chicken tikka masala: Stir in heavy cream, season with salt and pepper, and simmer until sauce is thick and creamy. Add chicken broth gradually if the sauce is too thick.
Warm naan: Heat naan in a skillet over medium heat for 30 seconds per side. Cut into wedges.
Serve: Plate chicken over rice, garnish with cilantro, and serve with naan and coconut water.