When you like GTK(3), you may convert tutorials from Python, Ruby, Vala, C++. That is easy. But I don't think that is what you want.
There seems to be some wrapper support for Qt Qml, maybe that is what you like better. I am not sure what Qml is exactly, but maybe you can find a tutorial.
For other GUIs, you may better create the bindings before writing a tutorial.
@Stefan Qml is a declarative language for creating modern UI. In reality is more a mix of declarative and imperative given that you can use Javascript. Basically QML is a better XAML (if you know microsoft stuff)
@Daimon the current DOtherside doc is fairly well written an procede in a step by step way. Here the link http://filcuc.github.io/DOtherSide/