Button with gradient and round courners doesn't show text

ButtonProblemSample.swift

import UIKit

extension UIButton {
    
    func applyBackgroundGradientStyle()  {
        roundCorners()
        applyGradient()
        self.setTitleColor(UIColor.white, for: .normal)
    }
    
    private func roundCorners() {
        self.layer.cornerRadius = self.frame.size.height/2
        self.clipsToBounds = true
    }
    
    private func applyGradient()  {
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = self.bounds
        
        let startColor = UIColor.red.cgColor as CGColor
        let endColor = UIColor.blue.cgColor as CGColor
        gradientLayer.colors = [startColor, endColor]
        
        gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
        gradientLayer.endPoint = CGPoint(x: 1, y: 0.5)
        
        gradientLayer.locations = [0.0, 1.0]
        
        self.layer.insertSublayer(gradientLayer, at: 0)
    }
    
    //If I comment this function, the title will apear, but the gradient doesn't have the correct frame
    override open func layoutSubviews() {
        super.layoutSubviews()
        if let subLayers = self.layer.sublayers {
            for layer in subLayers {
                if layer is CAGradientLayer {
                    layer.frame = self.bounds
                }
            }
        }
    }
}

let button = UIButton(frame: CGRect(x: 0, y: 0, width: 100, height: 20))
button.setTitle("Button", for: .normal)
button.applyBackgroundGradientStyle()
button.frame = CGRect(x: 0, y: 0, width: 200, height: 40)
button