Apex domains cannot have CNAME records.
Question and response
Question
dig principalpipe.com. NS
Answer
principalpipe.com. 5 NS ns1.principalpipe.com.
principalpipe.com. 5 NS ns2.principalpipe.com.
Authority
The response has no authority records.
Additional
ns1.principalpipe.com. 5 A 173.44.187.104
ns2.principalpipe.com. 5 A 51.91.165.230
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0