Heat the oil in a large frying pan and add the cumin seeds. Stir on medium heat for about 1 minute, until fragrant. Add the onion, garlic and chilis to the pan. Cook, stirring occasionally, for 5 to 7 minutes or until the onions have softened.
Stir the ginger, garam masala, coriander, turmeric and salt into the pan and continue cooking for an additional minute.
Add the chickpeas, water and the tomatoes, along with their liquid, to the pan. Stir to combine and bring to a simmer.
Reduce the heat to medium low and continue cooking, stirring occasionally, for about 20 minutes. The sauce will thicken.