In a medium bowl, whisk together the Greek yogurt, lemon juice, and turmeric until smooth.
Cut the chicken breast into bite-sized pieces and toss in the yogurt mixture to coat thoroughly; let marinate for 15 minutes.
Heat the ghee in a large skillet over medium heat, then add the diced yellow onion and sauté until translucent and fragrant.
Stir in the minced garlic and grated fresh ginger, cooking for 1 minute until the aromas are released.
Add the garam masala and cumin to the skillet, stirring constantly for 30 seconds to toast the spices without burning them.
Pour in the tomato puree and bring the mixture to a gentle simmer.
Add the marinated chicken pieces and any remaining marinade into the skillet, stirring to combine with the sauce.
Cover and simmer for 10-12 minutes, or until the chicken is cooked through and the sauce has thickened.
Stir in the full-fat coconut milk to create a rich, creamy texture and season with sea salt and black pepper.
Garnish with freshly chopped cilantro before serving.