1. In a large pot, heat the oil over medium heat. Add the cardamom pods and cumin seeds and toast for 30 to 45 seconds. Add the onion, chili, garlic, and ginger. Cook until the onion begins to caramelize around the edges, seven to eight minutes. Add the turmeric, ground cumin, chili powder, coriander, and salt and black pepper to taste and sauté for one minute. Add the tomato paste and cook until it has darkened, about three minutes.
2. Add the puréed plum tomatoes and bring to a boil over medium-high heat. Reduce the heat to low and simmer, stirring often, until the sauce thickens, five minutes. Add the reserved marinade and cook until the mixture is slightly reduced, 10 minutes. Add the cooked chicken, coconut milk, lemon juice, and sugar, then cook until the chicken is opaque, 10 minutes more. Sprinkle the chopped cilantro on top. Serve with garlic naan on the side.