In a large bowl, combine Greek yogurt, lemon juice, ginger-garlic paste, turmeric, garam masala, ground cumin, ground coriander, smoked paprika, chili powder, salt, and a drizzle of oil. Mix until smooth. Add chicken pieces, ensuring they are coated. Cover and refrigerate for at least 1 hour, preferably overnight.

Preheat grill pan over medium-high heat. Add a splash of oil and sear marinated chicken for 4-5 minutes on each side until cooked through, or bake in the oven at 400°F for 15-20 minutes.

In a large pan, melt butter or ghee over medium heat. Sauté finely chopped onions until golden brown, about 5-7 minutes, then add garlic and ginger, cooking for another minute. Stir in tomato paste and crushed tomatoes, cooking for 8-10 minutes.

Lower heat and add grilled chicken to the pan, ensuring each piece is well-coated. Let simmer for 5 minutes. Stir in heavy cream or coconut milk, adjusting seasoning, and finish with extra lemon juice and cilantro.