In this teshuva, Rav Yosef deals with the issue of whether or not it is possible to kasher frying pans or cake pans via hag'ala. One aspect of the issue is to what degree are such pans considered to be cooked in while dry, and to what degree do we could the oil as a liquid that is always present in the pan? Rav Yosef concludes that frying pans can be kashered via hag'ala, although they need to be well scrubbed first.
In terms of cake pans, Rav Yosef notes that even though such pans are sprayed first with some oil-like substance, that oil is minimal and does not count as a liquid vis-a-vis the method of cooking. Furthermore, since such pans, particularly aluminum ones, cannot withstand the heat of libun, it is best to store them away over Pesach.