Apex domains cannot have CNAME records.
Question and response
Question
dig pidom.com. NS
Answer
pidom.com. 5 NS ns0.transip.net.
pidom.com. 5 NS ns2.transip.eu.
pidom.com. 5 NS ns1.transip.nl.
Authority
The response has no authority records.
Additional
ns0.transip.net. 5 A 195.135.195.195
ns1.transip.nl. 5 A 195.8.195.195
ns2.transip.eu. 5 A 37.97.199.195
ns0.transip.net. 5 AAAA 2a01:7c8:dddd:195:0:0:0:195
ns1.transip.nl. 5 AAAA 2a01:7c8:7000:195:0:0:0:195
ns2.transip.eu. 5 AAAA 2a01:7c8:f:c1f:0:0:0:195
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0