Apex domains cannot have CNAME records.
Question and response
Question
dig 2is.nl. NS
Answer
2is.nl. 5 NS nsplus5.2is.nl.
2is.nl. 5 NS nsplus7.2is.eu.
2is.nl. 5 NS nsplus6.2is.be.
Authority
The response has no authority records.
Additional
nsplus5.2is.nl. 5 A 208.94.148.13
nsplus6.2is.be. 5 A 208.80.124.13
nsplus7.2is.eu. 5 A 208.80.126.13
nsplus5.2is.nl. 5 AAAA 2600:1800:5:0:0:0:0:1
nsplus6.2is.be. 5 AAAA 2600:1801:6:0:0:0:0:1
nsplus7.2is.eu. 5 AAAA 2600:1802:7:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0