Preheat oven to 450 degrees.
If using dried chickpeas: Bring 6 cups water to a boil. Pour boiling water over chickpeas and soak for 1 hour. Drain chickpeas from soaking water and boil in new water for about 20 minutes until soft.
If using canned chickpeas, drain and transfer to a clay pot or heavy baking dish.
Add garlic and rosemary leaves, then stir to distribute.
Massage onions with extra-virgin olive oil until slightly softened and add to the chickpeas along with grape syrup. Mix to combine.
Cover the pot with foil and bake for one hour; remove cover and bake for another 30 minutes uncovered. Stir from time to time if onions are burning.
Finish by topping with a drizzle of olive oil, freshly squeezed lemon juice, and lemon zest. Season with salt and pepper to taste.
