Mix the cumin, smoked paprika, curry powder, cayenne pepper, salt chicken seasoning into a small bowl. Separate half the spice mix into another large mixing bowl. Add the yogurt and lemon juice to this bowl and mix well.
Toss the chicken in with spiced yogurt marinade. Let it sit for 1 hour or overnight.
When ready to cook the chicken, heat an oiled caste iron grill on stovetop. Remove most of the marinade from the pieces of the chicken before cooking.
Grill the chicken in batches until just cooked through.
In a large saucepan on medium high heat, add the butter, chopped onion and let brown.
Add the ginger and garlic and rest of the spices, stirring well for 30 seconds until you can smell them well.
Add in the tomato paste, coconut milk, heavy cream, stir and let simmer on a low-medium heat for 7-10 minutes.
Add the chicken to the sauce and stir well. Garnish with fresh cilantro leaves.
Serve with warm store-bought naan bread and tamarind sauce.