Use NLog as OWIN logger factory

startup.cs

// first install the Nuget Package with:
// Install-Package Pysco68.Owin.Logging.NLogAdapter

// add this reference
using Pysco68.Owin.Logging.NLogAdapter;

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        // here's the magic
        app.UseNLog();
    }
}