I recently asked for a well done steak at a restaurant, while my friend asked for a medium rare. When waiter came back with two steaks, he used 「火をよく入れた方」 to let us know which one is well done. So essentially it was used as "the one cooked longer".
I then tried to re-use this expression at the other restaurant in the same situation, with the only difference that now I was supposed to tell waiter what kind of steak I'm expecting (so that he could give me the right one out of two he brought). And he didn't get what I meant.
I later asked my Japanese colleague about this expression and he claimed that it is not a standard thing to use 火を入れる in such context. However, searching on the Internet gives me following examples, which reassures me that waiter from the first restaurant was not wrong:
Could it be that this expression when used in context of frying meat is a professional slang of some sort? Any advice would be appreciated.