Can't clean cast iron pan
Years ago I bought a Lodge cast iron pan, used it once, and burnt something really badly, leaving a burnt residue behind. I tried cleaning it at the time, but couldn't penetrate the surface of the burn mark.
Fast forward to today, I decided to finally dig it out from storage and have another go at it. I scrubbed with a brillo pad for
hours minutes, and just managed to get some of the residue off, but it seems that no amount of scrubbing will get it all off (see photos).
Is there another trick to getting this clean so I can finally re-season it and start using it again? Would baking it in the oven help? Or would that just make things worse?