In a small bowl, whisk together the Greek yogurt, lemon juice, half of the garam masala, and all of the turmeric until smooth.
Cut the chicken breast into bite-sized cubes and toss in the yogurt marinade; allow it to sit for at least 15 minutes in the refrigerator.
Heat the ghee in a large skillet over medium-high heat and sear the chicken pieces until golden on all sides, then remove the chicken and set it aside.
In the same skillet, add the diced yellow onion and sauté until translucent and soft.
Add the minced garlic and grated fresh ginger to the skillet, cooking for 1 minute until fragrant.
Stir in the tomato puree, the remaining garam masala, cumin, sea salt, and black pepper, then let the sauce simmer for 5 minutes.
Reduce the heat to low and stir in the full-fat coconut milk until the sauce is creamy and well combined.
Return the seared chicken to the skillet and simmer gently for 3-5 minutes until the chicken is cooked through.
Serve the warm chicken tikka masala over the cooked basmati rice and garnish with fresh chopped cilantro.