Why does setting a scene's background to .clear draw a black box.

I have a scene on top of the main ViewController. While that scene will have objects in it, I'd like the background to be clear.

However
Code Block
        myView.backgroundColor = .clear
        myView.allowsTransparency = true

produces a black box.

Am I missing some step?
Why does setting a scene's background to .clear draw a black box.
 
 
Q