For chicken and marinade:
Combine chicken, lemon juice, garlic, 1 tbsp garam masala and 1 tsp salt. Marinate for 30 minutes to 1 hour.
For sauce:
Heat oil in a large skillet over medium heat. Add onions and cook for 5-7 minutes until softened.
Add garlic, 2 tbsp garam masala, paprika, cinnamon and 2 tsp salt. Cook for 1 minute.
Add tomatoes and simmer for 10 minutes.
Stir in cream and butter. Simmer for 5 more minutes.
Add chicken and marinade to the sauce and simmer for 15-20 minutes until chicken is cooked through.
Garnish with chopped cilantro (optional).
