In a bowl, combine the chicken pieces with yogurt, lemon juice, cumin, coriander, turmeric, garam masala, chili powder, garlic, ginger, and salt. Mix well and marinate for at least 30 minutes, or overnight for best results.
Heat vegetable oil in a large pan over medium heat. Add the onions and cook until softened, about 5 minutes.
Add the garlic and ginger, and cook for another 1-2 minutes until fragrant.
Stir in the diced tomatoes and cook for 5 minutes, allowing the flavors to combine.
Add the marinated chicken pieces to the pan and cook for about 10 minutes, until the chicken is cooked through.
Stir in the heavy cream, cumin, coriander, garam masala, turmeric, and chili powder. Simmer for 5 minutes, adjusting salt and pepper to taste.
Garnish with fresh cilantro and serve with rice or naan bread. Enjoy your flavorful Chicken Tikka Masala!