Change @RenderBody to point to a different view of MVC3

He does not point to this view, he simply displays the view that he is given

Your application launches and proceeds to the default routing action, which can be found in Global.asax

You can change this default value to /Account/LogOnif you want

public class MvcApplication : System.Web.HttpApplication {

    public static void RegisterGlobalFilters(GlobalFilterCollection filters) {
        filters.Add(new HandleErrorAttribute());
    }

    public static void RegisterRoutes(RouteCollection routes) {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
        //routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" });

        routes.MapRoute(
            "Default", // Route name
            "{controller}/{action}/{id}", // URL with parameters
            new { controller = "Account", action = "LogOn", id = UrlParameter.Optional } // Parameter defaults
        );
    }

    protected void Application_Start() {
        AreaRegistration.RegisterAllAreas();

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);
    }
}