I solved it. The issue was that, when I created the site, I updated all packages via Nuget. However, as I wasn´t going to use Entity Framework, I uninstalled it. In order to be able to uninstall that package, it required for me to uninstall Microsoft.AspNet.Providers.Core 1.2 as well… and I did.
This missing package messed things up. I cleared the project and started all over again. I could have also used the Update-Package command in the PM Console and would have restored all lost packages. However, since I had done so much mess compared to the little (next to null) work I had done, I decided to start it all over again.
Thanks anyway!