Chicken tikka masala is meant to be rich and buttery. Chef Saran begins by marinating chicken in yogurt with ginger, garlic, cayenne, and garam masala before simmering it in cream with cinnamon and other spices.
Peel and chop onion, garlic, and ginger. Place in a food processor along with the yogurt, cayenne and garam masala. Process until smooth. Combine the marinade with the chicken and refrigerate at least 1 hour and up to overnight.
Preheat oven to 350 degrees F. Once chicken has marinated, place in a single layer on a drip tray set over rimmed baking sheet (or a foil-lined baking sheet). Bake 15-20 minutes. Meanwhile, make the sauce: Peel and cut the onion into large chunks, peel and chop the ginger, and smash the garlic with a knife to remove the skin. Place the onion, ginger, and garlic in a food processor and puree, then set aside. In a medium saucepan over medium heat, add oil, followed by the cinnamon stick. Add onion mixture and stir. Add a teaspoon of salt and continue stirring.
Continue cooking for 20 minutes until the mixture turns a light golden brown. Keep a cup of water beside the stove while the onion cooks. When the onion begins to stick, add water, about 1 teaspoon at a time, and scrape the bottom of the pan to pull up the brown bits and keep the onion from burning. Add turmeric, coriander, cumin, and cayenne; mix and cook for a minute or two. Add a bit more water and continue stirring. Stir in tomato puree and season to taste with salt. Stir in the cream, turn off the heat and set aside.
Place cooked chicken into the sauce and gently mix in the pan over low heat. Mince cilantro stems, sprinkle on top, and serve.