An old trick( from the 1940s allegedly) is to boil up some rhubarb in the pan. The acid is supposed to help get burnt residues off. Rhubarb just coming into season now!
For any cooked on food like that, I put some dishwasher powder into the pot and half fill with water, then boil the pot. Bingo, all baked-on food and stains disappear.
The other day I left some apple stewing and forgot about it! Result big soup pot with non stick coating blackened! I have scrubbed some off and left it to soak with bicarb of soda. Still only partially clean. Any advice/ suggestions please? Would stewing rhubarb in it work??