Does the effect make its cause? Does a cause depend on its effect? If so then it seems especially difficult to think about nothingness being made or created.

This is almost the exact opposite of a question I have asked recently (I'm locked out and looking into that), but not quite.

It's usually said that the cause does depend on the cause, in some way


  Nāgārjuna argues that cause and effect cannot be substantially
  distinct. This is because the effect depends existentially on the
  cause (if the cause did not exist the effect would not exist) and
  cause depends at least notionally on the effect (if there was no
  effect the cause would not be called “cause”). The kind of
  independence demanded by substantial existence, by existence by
  svabhāva, is simply not available for things which are cause and
  effect.


But what this notional dependence means I'm not totally sure.

I'm not asking about nothingness, and am not saying that sunyata is nothingness! That could only be the case if the absolute truth is that nothing exists.
Cause and effect are mutually dependent like father and son. If there is no son there is no father, and if no father then no son. 

In this way Nagarjuna proves the non-existence of these things except as appearance/emptiness. 

He explains that the cause cannot exist prior to the effect, the effect cannot exist prior to the cause and they cannot come into existence simultaneously. Ergo, it's all smoke and mirrors.