This HaBO is from Liz, who is hoping to find this contemporary (at least I think it’s contemporary):
I’ve been wracking my brains trying to remember a book title, and someone just directed me here!
Ages ago I read a romance novel where the male lead was secretly a romance author, and the female lead was the editor of the author, having no idea the author was a guy. Her job is on the rocks after she refused a manuscript from another popular author, and then she gets a note from the male lead saying that he is taking a break from writing. Editor goes in search of author to beg the author to continue writing, encounters male lead, who promises to help her (while not letting on that he is really the author in question).
There are a few books where the hero is secretly a romance author, but I haven’t read them, so I can’t say for sure which one it is.