If it is still hot, it will be really snug because of material expansion. don't open if its hot anyway.
If not, try a strap wrench. I believe thats what they are called anyway. It has a leather or rubber strap that can be wrapped and tightened down on what object you desire.
If you don't have on, maybe a 1 and 1/2 in socket? lol Use whatever size the cap is.
Giant vise grips or channel locks with work as well.
