InvalidArgumentException Mailer [mail] is not defined.

When i register a new user

protected function create(array $data)
    {
        $user = User::create([
            'name' => $data['name'],
            'email' => $data['email'],
            'username' => $data['username'],
            'password' => Hash::make($data['password']),
        ]);

        $userRole = Role::select('id')->where('name', 'user')->first();
        $user->roles()->attach($userRole);

        $email = $data['email'];
        
        $data = ([
        'name' => $data['name'],
        'email' => $data['email'],
        'username' => $data['username'],
        ]);
        
        Mail::to($email)->send(new WelcomeMail($data));

        return redirect('/login')->with('message', 'Account created successfully, Congratulations');
    }

Mail

public function __construct($data)
    {
        $this->data = $data;
    }

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        $subject = 'Welcome';
        return $this->view('emails.welcome')->subject($subject);
    }