In a baking dish, toss together the chicken, yogurt, garlic, ginger, garam masala, cumin, turmeric, cayenne pepper, and 1 teaspoon salt. Let sit 5 minutes. Preheat the oven to 400°.To the chicken, add the onion, then pour over the coconut milk. Add the tomato paste. Stir until creamy and well-mixed. Arrange the butter slices over the chicken. Sprinkle with sesame seeds. Bake 30-40 minutes, until the chicken is cooked through. Top with cilantro. Meanwhile, melt the butter, chili flakes, and paprika together. Cook until the butter is browning. Remove from the heat.Serve the chicken and sauce over bowls of rice with chili butter and naan. Enjoy!