Put tomato chunks in a deep saucepan along with a pinch of salt. Sprinkle a little water over chunks. Place saucepan over a medium flame and bring to a boil. Stir often till tomatoes are reduced to a pulpy consistency. Most of the water should have dried up. Puree in a processor or blender. Keep aside.
Heat ghee in a deep saucepan. When it shimmers drop red and green chiles, mustard and cumin seeds and curry leaves. Wait 20 seconds to let sees splutter, then add tomato pulp and stir well. Let tomatoes stew for a few minutes.
Add coconut milk to tomatoes along with salt. Lower flame and let the Saar come to slow boil for 5 minutes.
Garnish with fresh cilantro and serve with rice or parathas. Or even a chunk of toasted sourdough.