Recursive CTE to find unique slug

I have an article table where I want the slug to be unique.

CREATE TABLE article (
   title char(50) NOT NULL,
   slug  char(50) NOT NULL
);

When the user enters a title e.g. News on Apple, I want to check the database to see if a corresponding slug exists e.g. news-on-apple. If it does, I'll suffix a numerical value until I find a unique one e.g. news-on-apple-1. Can that be achieved with a recursive CTE query instead of doing recursion in my ORM. Is there a good ballpark number where I should stop recursing and error out. I can imagine people using the same title a 1000 times which would result in 1000 queries just to create 1 article.

It's possible that my understanding of recursive CTE is incorrect and there's no better way to find a unique slug. Please suggest any alternatives.