MB3 136b: Adding Salt and Spices to Hot Food on Shabbos (318:9-10)

A kli rishon can cook an item even if not on the fire if it's יד סולדת בו. If a kli is on the fire salt and spices can't be added. A solid item in a kli sheni that is יד סולדת בו. Putting sugar in a kli rishon. Pouring from a kli rishon onto spices.