"Porting" is a term generally used to describe the process of taking an application designed to run on one hardware platform to another and usually used when talking about moving games to other systems.
From a brief look at the page you linked, Haml is used in relation to Rails development - so I suspect that your question hasn't actually got anything to do with translating Haml to HTML, but rather how to easily move a web based application developed using Rails to .NET. The quick answer will be that you can't... any sort of 'automatic' conversion is going to fall short of what you're after.
If you are looking to move an app across to .NET, your best bet is to map the functionality of the current app and re-create it from scratch.... trust me, it'll be quicker with a better end result.
