Cold water to cool the burn and stop it from getting worse. If it's really bad you may need to see a doctor but for most burns cooling it immediately with cold water and keeping it protected and clean afterward is all you can do. Ice may ease the pain while you wait for it heal.
Butter or other oily/greasy stuff has been found to be worse than doing nothing.
I'm an emergency doctor and moonlighted immense hours at Temple Hospital Burn Center during my training.
Please, do not put toothpaste or any other home remedy on any sort of burn. I won't go into all the details of burn care and the kinds of burns but tell you just the basics.
Burns are treated with infection prevention and pain control. Putting cold water on a burn does not do anything but get it wet and clean. Having said that, cleaning a burnt area immediately is quite useful and the cold water can sometimes help the pain temporarily. If the area is mildly painful and a bit red, just let it be. Covering it with a band-aid can help prevent you from knocking it into things and causing more pain. If the area is very painful with a blister or a bit pale, be sure to keep it covered with a bandage and antibiotic ointment. If ibuprofen (if your health allows you to take it) or Tylenol doesn't alleviate the pain to a tolerable level, you may need to see a doctor for better pain control (e.g. narcotics).
Good luck to you and I hope the cookies are delicious!
P.S. the cookies tased great!!!