Blowtorch on full power
Shots like these used to drive me absolutely insane. Anyone that used a blowtorch before would tell you that the inner cone might be visible, but the outer cone is very faint (and, a quickie science class here: The hottest part of the flame is at the tip of the inner cone).
To shoot this shot, I turned off my shop lights (and make my way back to the torch, very careful not to trip over my camera - or worse, topple the tripod with my camera and poverty wizard multimax into the blow torch). Now, my ambient light is my flame and I can expose for that without worrying about blowing anything else out. Finally, to capture the rest of the scene (torch, canister, etc) I use a strobe softened with a brolley, and just adjusted power accordingly to give myself a good exposure on the can and background.
I think on camera flash would have killed the cherry red hot tip.
Strobist:
580EX II M 1/32 Brolleyed cam right