Button renderer iOS

Hi,

I'm new to Xamarin and start with Xamarin.Form API. I look video for using renderer to customize each component for each platform.
I try to make a button with a background gradient but can't find how do it iOS cause my component is a button and not an UIButton so I can't use CAGradientLayer to make it.

Did anyone can help me ? Maybe is there a way to retrieve an UIButton instead of a Form.Button element.