Add the tomatoes, stir and cook two minutes. Now add the chickpeas with their liquid, 2 1/2 to 3 cups water, the salt, garam masala, amchoor, cumin seeds and cayenne pepper. Stir to combine and bring to a boil. Reduce heat to low and simmer gently for 15 minutes. Stir in most of the fresh coriander, leaving just a little for the final garnish.