Marinate the Chicken: In a bowl, mix Greek yogurt, lemon juice, ginger-garlic paste, turmeric, garam masala, ground cumin, coriander, smoked paprika, chili powder, and salt. Coat the chicken thoroughly, cover with plastic wrap, and refrigerate for at least 1 hour.

Cook the Chicken: Preheat your grill or oven to 400°F (200°C). Grill the marinated chicken for 4-5 minutes on each side until charred and cooked through, or bake on a lined sheet for 15-20 minutes, flipping halfway. Let rest before preparing sauce.

Prepare the Masala Sauce: In a skillet over medium heat, melt butter or ghee. Add chopped onions and sauté for 8-10 minutes until golden. Stir in garlic and ginger, cooking for another 2 minutes until fragrant.

Toast the Spices: Add turmeric, ground cumin, coriander, garam masala, and smoked paprika to the onion mixture, stirring for 30 seconds. Stir in tomato paste and crushed tomatoes, blending until smooth. Let simmer for 10-15 minutes until thickened.

Combine Chicken and Sauce: Add the grilled or baked chicken pieces to the pan. Simmer on low heat for 5 minutes, adjusting thickness with a splash of water if necessary.

Finish with Cream and Garnish: Stir in heavy cream or coconut milk, heat for another 2-3 minutes, and add sugar if desired. Garnish with fresh cilantro and a squeeze of lemon juice before serving.