Heat the oil in a large heavy-bottomed pan over medium heat, then add the cumin seeds and cook until they crackle and release aroma, about 30 seconds.
Add the chopped onion to the pan and sauté until translucent and golden, about 5–7 minutes, stirring regularly. The kitchen should smell sweet and warm.
Stir in the grated ginger and minced garlic, cooking until fragrant, about 1 minute. The mixture will become more aromatic and slightly bubbling.
Add the ground coriander, turmeric, and a pinch of cinnamon to the pan, stirring briefly until the spices release their aroma, about 30 seconds.
Pour in the diced tomatoes and cook, stirring occasionally, until the mixture thickens, darkens slightly, and becomes jammy, about 10 minutes. You’ll notice a rich, warm aroma filling the kitchen.
Add the cooked chickpeas to the pan, stirring well to coat them in the tomato-spice mixture. Let everything cook together for 5 minutes, allowing flavors to meld.
Pour in the coconut milk, stirring gently as it combines with the spices and chickpeas. Bring to a simmer, then reduce the heat to low and cook for 10–15 minutes until the sauce becomes thick and glossy.
Remove the pan from heat, squeeze in the juice of the lemon, and stir. Taste and adjust seasoning, adding salt if needed. The sauce should be smooth, fragrant, and cling to the chickpeas.
Garnish the curry with chopped fresh cilantro just before serving. Serve hot with rice or flatbread, spooning generous portions into bowls.
