ViewRenderer SetNativeControl

I am going crazy trying to find the answer to this and having old posts about using NativeRenderer isn't helping!

I want a simple custom view to display lines that I draw in native code.
I have added to my xaml

xmlns:local="clr-namespace:ExecutiveScanner;assembly=ESXamlFormsPCL"
and
 <local:SpectrumView />

I have added to my xaml.cs

public class SpectrumView : View { }

and in my iOS I have

[assembly: ExportRenderer(typeof(SpectrumView), typeof(SpectrumRenderer))]

and

   public class SpectrumRenderer : ViewRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<View> e)
        {
            base.OnElementChanged(e);
            if ((e.OldElement != null) || (this.Element == null))
                return;

            if (Control != null)
            {
                Control.BackgroundColor = UIColor.Red;
            }

            SetNativeControl(new UIView());
        }

        public override void Draw(CGRect rect)
        {
            base.Draw(rect);


            var context = UIGraphics.GetCurrentContext();

            context.SetLineWidth(4);
            UIColor.Red.SetFill();
            UIColor.Blue.SetStroke();

            var path = new CGPath();

            path.AddLines(new CGPoint[]{
                new PointF(100,200),
                new PointF(160,100), 
                new PointF(220,200)
            });

            path.CloseSubpath();

            context.AddPath(path);
            context.DrawPath(CGPathDrawingMode.FillStroke);
        }
    }

Without SetNativeControl I get an Exception when it tries to display the page but what di I use for this ?
With new UIView() it doesn't call Draw! Should I use a different Native Control ? Should I create my own (How ?) or should I be using something other than Draw ?
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Thanks for any help you can offer.
Wayne