I'm afraid I can't help on this one, but it is a great question. I used to run internal classes on precisely this subject as we had a lot of junior devs coming in who knew this framework or that framework and really had no idea how the web actually works. (Unfortunately the content I used was left at that company.)

One thing I would emphasise is the importance of HTTP - and whilst I wouldn't recommend anyone actually reading a formal spec from beginning to end, if you really do understand request-response mechanics it will underpin everything else you learn (which is essentially how to process requests and generate responses).