How to set the Canvas to fill screen in landscape mode?

I am trying to build a game in landscape mode using Canvas and I am not able to fill the canvas to the entire screen. I am testing on iPhone and Ipad and see the screen as below.

In the Advanced settings of Canvas → Positioning, I have set the position to Relative.
Can you please help me out with this - I want the canvas to fill the device’s screen ( without the white spaces)

Bumping this up to see if there are any suggestions please…