How to access a JFrame from anonymous ActionListener for adding a panel in frame?

I want to add a JPanel in a frame if a certain button is clicked and I don't know how to manage that from an anonymous ActionListener. Here is the code:

public class MyFrame extends JFrame {
   JPanel panel;
   JButton button;
   public MyFrame() {
      button = new JButton("Add panel");
      button.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent event) {
            panel = new JPanel();
            //here I want to add the panel to frame: this.add(panel), but I don't know
            //how to write that. In these case "this" refers to ActionListener, not to
            //frame, so I want to know what to write instead of "this" in order to
            //refer to the frame
         }
      }
      this.add(button);
  }

Thank you in advance!