开锅 can refer to a antioxidation and coating procedure using heat and oil for pure old-fashioned iron and steel pans and pots. Here 开 takes its meaning of a procedure "to initiate". Similar usage is in 开业、开张、开盘，which mean "to open business," "to open business", and "to open quotation on the stock exchange," respectively. Many demonstration videos can be found YouTube https://www.youtube.com/watch?v=B82JD32V8aY. Note that this procedure is not applicable to most modern kitchenware with composite coating.
开锅 can also refer to the action of removing the lid of a pot. Here 开 takes its meaning of an action "to open something with a cover". Similar usage is in 开窗、开门、开箱，which mean "to open a window," "to open a door", and "to open a package and present the content," respectively.
Baidu apparently tracks the usage frequency among Chinese better than Google because 开锅 is lately mostly a key word of many short videos that demonstrates the antioxidation and coating procedure, whereas "the action of removing the lid of a pot" does not as easily find a situation to express online. However, neither can be yet used as a reliable source of Chinese-English translation as the machine learning algorithms require huge input data, while high-quality human-examined translation has not received enough treatment.
By the way, I am somewhat surprised that HSK 5 is still addressing text like a cookbook. Such text reads like Grade 2-3 for native speakers.