CommonName is deprecated for matching names on x.509 certificates used for TLS, and has been deprecated for like 18 years now. Let’s Encrypt just puts the first name on the certificate in that field. SubjectAlternativeName is the field that matters.
That being said, I think you can force this by re-issuing your certificate with the --cert-name parameter, but I’m not positive that actually affects the CN as opposed to simply affects housekeeping for Certbot.
EDIT: You’re not using Certbot, my mistake. Didn’t read close enough. You’d have to check with the developer of whatever cPanel tool you’re using to issue these certificates for how to determine CN, but I wouldn’t be surprised if you’re not going to be able to change this.
It looks to me like the certificate was created by BlueHost. In that case it’s up to BlueHost’s discretion which name they request as the CN. Since Let’s Encrypt has rate limits
hosting providers aren’t necessarily able to give every customer their choice of a CN (although this is more likely to be a consequence of the hosting provider’s choice of tools rather than of the Let’s Encrypt rate limits).
As @jared.m mentioned, the CN field no longer has any technical significance. Some people don’t like the way that it may show curious site visitors that your site is hosted on shared infrastructure together with other sites, but this situation is very common—and becoming more common over time!—unless you’re using a VPS or dedicated server.
