[smt88]

> Do you think learning a new stack because of a fashion is valid reason ?

Yes!

> so back-end is going to be a REST Api with ASP.Net Web Api secured with OWIN/Katana

REST APIs are what Node is best at! You should definitely at least try to write your API in Node.

> I slightly disagree your find an existing framework and continue approach. Because in my opinion if i code everything i will learn more

You will learn more if you code everything, but you're also not learning from the wisdom of the community. Node is used in a very different way from ASP.NET, Python, PHP, etc. You should learn "the Node way". It's always better to learn how each language does things rather than trying to recreate another environment that you're already used to.

Since this is just for the presentation layer, your Node code would be absolutely tiny -- you're not going to learn very much anyway.

I'd suggest using Express. Most Node servers, especially small ones, are based on Express anyway.