Show a Toast message from inside uiThread Runnable?

I want to show a toast message from within a thread that is running on the UiThread however it appears the Runnable is not referenced correctly in my call. Please see my very basic implementation below:

this.runOnUiThread(new Runnable() {
     public void run() {
                Toast.makeText(this, "Authenticated.", Toast.LENGTH_SHORT).show();
            }
        }
);

I believe that this is not the actual runnable that the makeText function requires. How would you get the actual Runnable in this case?