Question: This question has come from a conversation at loggerheads. I can't find the answer online.
There are two positions on which is the correct expression to use when starting a job.For the example, I've used a job as a plumber.

Person A states "John becomes a plumber today"
Person B states "John has started working as a plumber today".

My understanding is that person A, while it is used in causal conversations is incorrect because it suggests a changing into something when they haven't changed, they added something to who they are. A job.
Can someone please advise which is formally correct and if using becomes is still incorrect use of the word or how they fit together.

Answer: 
To "cut to the heart of the matter" is an idiom that means "get straight to the point". But "cut to the heart" can also mean to strongly engage someone's emotions, as a song might do.

Which meaning applies would depend on context.
"To cut to the heart" could mean different things in different contexts. For example it could be a poetic way of saying "When you attack someone, you hurt them very badly", or perhaps, using the metaphor "the heart of the problem" (meaning the most important aspect), "When you analyse a problem, you immediately see the most important aspect of it".

So, the author is saying that the ability to **always** do this is a **sort of genius**, ie requires exceptional skill and is a very rare ability.

In this case, it appears that the problem that he "cuts to the heart of" is "to communicate very directly and with the utmost truthfulness".