1. Toast the cumin seeds in a dry frying pan/skillet for two minutes, tossing the pan/skillet occasionally, until they smell aromatic. Tip into a bowl and set aside.
2. Heat the oil in the frying pan/skillet over a medium heat and fry the onion for six minutes, until softened. Add the garlic and ginger and cook for another two minutes, stirring. Tip the onion mixture into the slow cooker pot with three-quarters of the toasted cumin.
3. Add the chickpeas/garbanzo beans, aquafaba, chopped tomatoes, chilli/hot pepper ﬂakes and turmeric. Cover and cook for four to five hours on low or three to four hours on high. Twenty minutes before the curry is ready, add the ground coriander, garam masala, lemon juice or tamarind and spinach. Stir until combined, then cover and ﬁnish cooking.
4. Serve topped with a spoonful of yogurt, coriander/cilantro, slices of red onion and sprinkled with the remaining cumin, with ﬂatbreads on the side.