Drawing shapes in Xamarin programmatically. Allow overlap and transparency

Question

I'm very new to Xamarin, but not C#. I'm trying to draw concentric circles and various shapes to a StackLayout, where traditionally I would use a Canvas in WPF.

I'm trying to avoid using SkiaSharp - and I wondered what control I should be using, if not a StackLayout? I can get it to draw shapes, but they clip one another and don't overlap as I want. See top left circles in image:

Any help would be really appreciated.