Heat the oil in a large skillet over medium heat. Add the cumin and coriander seeds and cook for about a minute, until aromatic and somewhat darker.

Add the onions and cook for about 5 minutes. Add water as needed to prevent the spices from burning. Add the garlic, ginger, and serrano peppers, and cook for one or two minutes, stirring frequently.

Add the ground spices and tomato paste. Stir frequently for a minute or two, adding water if needed to prevent the spices from burning. Add the tomatoes and salt. Use the released juices to deglaze the pan. Cook for five minutes, until the tomatoes are soft and start to release oil.

Add the coconut milk, chickpeas, tahini, and sugar. Adjust the consistency by adding water, a few tablespoons at a time, if needed. Simmer, covered, for 15 to 20 minutes. Stir occasionally.

Add the chard and cook for a few more minutes, until the leaves are tender. Add the garam masala, cilantro, mint, and lemon or lime juice. Season with salt to taste.