Heat the oil in a large pan over medium heat. Add the cumin seeds and let them sizzle for a few seconds until fragrant.
Add the chopped onions and cook until they turn golden brown, stirring occasionally.
Add the minced garlic, ginger, and green chilies. Sauté for another 2-3 minutes until the raw smell disappears.
Stir in the chopped tomatoes and cook until they soften and oil starts to separate from the mixture.
Add the turmeric powder, coriander powder, garam masala, ground cumin, ground coriander, red chili powder, and salt. Mix well and cook for another 2-3 minutes.
Add the cooked chickpeas and mix them well with the spice mixture.
Pour in the water and bring the mixture to a boil. Reduce the heat and let it simmer for 10-15 minutes, allowing the flavors to meld together and the sauce to thicken. Adjust the consistency with more water if needed.
Add the amchur (dried mango powder) or lemon juice and mix well. Taste and adjust seasoning if necessary.