Start by preheating your oven to 300 degrees and position the racks in the upper and lower thirds. Combine the chickpeas, ⅔ cup of olive oil, tomatoes, cinnamon, marjoram sprigs, and 2 tablespoons of chopped ginger on a sheet pan. Season this mixture with salt and pepper, then spread it evenly on the pan.
Scrub the squash well as the skin is edible, and use a paring knife to make a few pricks. Now, you can transfer the squash to an oven-safe skillet, a baking dish, or a second sheet pan (using foil will make cleanup easier). Coat the squash lightly with some oil, salt, and pepper. Bake the squash on the lower rack and the chickpeas on the upper rack. You'll want to keep them in the oven until a knife can easily pierce the squash, and the chickpeas and tomatoes have become dark red and thickened like jam. This should take approximately 2 to 2½ hours, and stir the chickpeas occasionally.
While the squash and chickpeas are baking, stir the remaining ½ tablespoon of ginger into the yogurt. Add water to thin it to your desired consistency, then season it with salt and pepper. Please keep it in the refrigerator until you're ready to serve.
Once the herb sprigs are removed, season the chickpeas with salt and pepper according to your taste. After the squash has cooled enough to handle, cut or tear it into large pieces, removing and discarding any stems, seeds, and stringy bits. Season the squash with salt and pepper. Place the squash pieces on a platter with the flesh side facing up, then top them with the chickpeas, some ginger yogurt, and a sprinkle of marjoram leaves. Serve the remaining yogurt on the side.