Apex domains cannot have CNAME records.
Question and response
Question
dig prtc.net. NS
Answer
prtc.net. 5 NS ns1.coqui.net.
prtc.net. 5 NS ns2.coqui.net.
Authority
The response has no authority records.
Additional
ns1.coqui.net. 5 A 196.28.61.33
ns2.coqui.net. 5 A 196.28.61.34
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0