This dish has become my favorite creamy tomato-based curry. It's the addition of the cardamom that makes this curry so fragrant. Traditionally, this curry is made with lamb. I recommend using lamb or beef, unless you want to keep it vegetarian, in which case tofu works well. If using tofu, I recommend making up the sauce a day ahead of time and marinating the tofu overnight. You can, of course, also marinate the meat ahead of time.