How do I change what email address the New Order email goes to?

When installing Commerce, a simple status workflow is created that includes emails to both the merchant (subject "New Order") and the client (subject "Thank you for your order"). 

The "New Order" email is configured to whatever is in the emailsender system setting at the time of installation. 

To change it later, go to Commerce > Configuration > Statuses. In the Status Changes column, click on Order Notification to Merchant to edit the email status change action. There you will find the Recipient field to change.