Did it leave any protruding you can get a hold of with a pair of small vice grips or is it flush/recessed?
If there is a bit sticking out you can get a hold of, you can carefully heat the area around the broken bolt with a propane torch (not oxy/acetylene!) and it should move. If flush or recessed, your only option is to drilled and attempt to use a small EZ-Out with heat. Drill small and if you have EZ-Outs use the smallest you can get away with and the correct size drill bit for the EZ-Out. If possible, center punch the broken bolt so you can drill the center of the bolt. If the drill wanders outside the steel bolt and into the aluminum cylinder material, there will be no bringing it back. You will probably be best off to remove the cylinder for this repair. If things go sideways, you may have to drill and tap to the next size up. It's a crappy scenario but sometimes that is the only/last resort rather than junk piling an entire cylinder.