Method not being called

I know I just posted, but I think my issue is something different now. I have created the simplest module I can think of with one function

<?php

if ( ! defined('EXT'))
{
    exit('Invalid file request');
}


class Commerce {
        
    var $return_data    = ''; 
    
    function Commerce()
    {
        echo 'This is the constructor';
    }
    
    
    function cart()
    {
        echo 'Cart function';
    }
    
}
// END CLASS
?>

I am calling it with the following tag:

{exp:commerce:cart}{/exp:commerce:cart]

I get the first echo statement, but not the second. The debug info is below.

(0.008304) Parsing Tags in Template (0.008331) Tag: {exp:commerce:cart} (0.008390) Closing Tag Found (0.008443) Processing Tags (0.008488) Module Tag: Commerce/cart (0.008503) Including Files for Tag and Modules (0.009902) Beginning Final Tag Data Processing (0.009928) Calling Class/Method: Commerce/cart (0.010012) -> Class Called: Commerce (0.010050) -> Method Called: commerce (0.010065) -> Data Returned (0.010119) - End Tag Processing - (0.010166) - End Template Processing -

What am I missing here? Thanks agan.