Maintain camera FOV & aspect ration without black bars

I’m working on some content which requires me to set a camera’s FOV and aspect ratio, and than set the view target to that camera.
Everything works fine except for the final result in the view target - I get black bars when the aspect ration doesn’t match the viewport size. However, I would like to remove the black bars and instead “stretch” the camera output, without changing the aspect ration.

This is how it looks with my desired FOV + aspect ration, with the black bars:

And this is what I would like to see:

Note: I cannot use scene capture 2d with some widget, I need the live camera output.

Would appreciate any help