Learn English – May I say something ‘has long been fascinating to me’

I have not eaten macaroons in a long time.

My preferred form.

It has been quite a long time since I've eaten macaroons.

I would remove the plural from this second one & recast it as

It has been quite a long time since I ate a macaroon

which would then make it quite OK.

This last one makes no sense at all

I haven been a long time no eaten macaroons.

This is to emphasis the word 'long'.

If you need to emphasize a specific fact or point in your text, there are several ways to focus the reader’s attention on it. This is one of those.

Eg:

It was the strangest piece of music I had ever heard.

Here, the word 'ever' is emphasized.