Drain and rinse the chickpeas. Reserving half a cup of cooking liquid for the dip.
Place the chickpeas in a large pot of water. Make sure there is about three inches of water covering the chickpeas at all times.
Bring to the pot to a boil, about 10 minutes.
Reduce to a simmer and cook until the chickpeas are soft, about 30 minutes.
While your chickpeas are cooking, slice the onions.
In a frying pan, saute the garlic cloves and onions in olive oil until they are caramelized, about 20 minutes. Add the saffron and cumin and cook for a further 5 minutes.
In a food processor, blend the chickpeas, caramilized onions with garlic, tahini, and lemon juice until smooth, about 5 minutes. Adjust the consistency with chickpea water.