Ask HN: What framework to use for side project.

Hi guys, So I'm thinking of starting a web application in my spare time as a side venture. Also using the experience to learn something new. I am a c#/java developer so I have experience with j2ee, mvc 4, and even play framework. But I was looking for something thats new/popular. I was thinking of using ruby on rails as I have heard some good things. But it seems to be going out of favour/security risks arising. Then I hear all these new things like node.js meteor and the likes. I dont want to use javascript as my server side code. Using it on the client side is enough :D. Thanks.