Best preventive measure, a crockpot, which is safe to leave without stirring.

First of all, remove immediately from the heat and pour WITHOUT STIRRING OR SCRAPING into a new pot.

If it is a beginning scorch, such as thick and brown at the bottom of a bean or potato soup,this may be all it takes.

Taste it. Cumin is helpful for mild scorches, whole cumin seed or mustard seed can be toasted in a dry skillet and stirred in, then simmered. Some people might use cayenne, this masks it somewhat,

At the next level is smoke seasoning or barbecue sauce. This works pretty well with bean soups, but add carefully a very little at a time. The other possibility is a can of concentrated onion soup, or dry onion soup packet.

If the soup is really burnt, compost it and make miso soup.

Better luck next time and keep on cooking- Ellen