Our website is hosted at webflow and uses the Cloudflare DNS.
We need to add another custom domain to the SSL certificate as a Subject Alternative Name, however on ordering an advanced certificate, the only option to add domains are for subdomains of the original domain.
How do we go about adding a completely new domain as a SAN?
You can not add a separate domain to a certificate. Cloudflare will only issue certificates for your current zones that are in Cloudflare.
Yeah Cloudflare only issues SSL certs for the one domain. The only way I can see it issue for another domain that isn’t a domain also on Cloudflare is if you add the domain as a custom hostname via Cloudflare For SaaS https://www.cloudflare.com/en-au/saas/. But not sure if that is what you want.
Blog article at https://blog.cloudflare.com/cloudflare-for-saas/