At what stage of research career one can write a 'tutorial article'?
Actually, I find that a relatively inexperienced (but not naive) person can write a valuable tutorial for novices. The reason is that they may remember how hard it was to get started and, especially, to gain insight. More experienced people, especially experts, often lose the sense of how difficult it once was.
I once specifically wrote a treatise on a topic I was learning in order to capture the wonder of it all along with the difficulty and what to look out for. It turned out pretty well.