Cron and request with wp_remote_post

I have a problem with a plugin I'm working on, I have implemented a cron that 2 times a day makes a call to update the data, the call is made with the wp_remote_post function.

$response      = wp_remote_post(
        ENDPOINT,
        array(
            'method'  = 'POST',
            'headers' = array(
                'Content-Type' = 'application/json; charset=utf-8',
                'domainUrl'    = get_site_url(),
            ),
            'body'    = wp_json_encode( $body ),
        )
    );

the problem is in the get_site_url() function.

For a site that uses the https protocol, get_site_url() returns the domain in https when the call is triggered from the frontend or wordpress hooks except cron, instead when get_site_url() is triggered by the cron hook it returns http. What may be causing this behavior and how I could fix it? Thanks