Frondoor Std/Premium TXT Domain validation lookup via CNAME

[matzter]

Hi, I'm not sure if there is a better place to ask my question as there is no frontdoor board in the techcommunity. 
Anyway, my question is about the TXT Domain validation process of frontdoor standard/premium.
I didn't find any hint about the concept of using CNAME records to support the TXT lookup. Does anyone know if this is supported in Azure Frontdoor?

Example:
Frontdoor is looking up the TXT entry "xyz123" on _dnsauth.www.test.com

I create a CNAME record _dnsauth.www.test.com pointing to _dnsauth.www.otherzone.com
I create a TXT record _dnsauth.www.otherzone.com with the content "xyz123".

Before you scream at me, please see https://letsencrypt.org/docs/challenge-types/ where this is supported.

Since Let’s Encrypt follows the DNS standards when looking up TXT records
for DNS-01 validation, you can use CNAME records or NS records to delegate
answering the challenge to other DNS zones.
This can be used to delegate the _acme-challenge subdomain to a validation-specific server or zone.
It can also be used if your DNS provider is slow to update, and you want to delegate to a quicker-updating server.

[#2 · Accepted solution]

I can actually answer myself on this, it works indeed.
The way we use this might be interesting for some of you, as in fact it allows you to easily plan and execute a DNS change that is independent from the actual setup.

Example:
With my application that uses frontdoor I deploy a separat DNS zone which is independent of the actual customer DNS. Then I tell the customer to create two CNAME records www.xyz.com and _dnsauth.www.xyz.com which point to www.mydnsrecord.com and _dnsauth.www.mydnsrecord.com. the mydnsrecord.com is the DNS zone I deploy with frontdoor, and create the TXT record for the certificate validation and the CNAME entry for the CDN endpoint. Works fine.