Apex domains cannot have CNAME records.
Question and response
Question
dig xtom.nl. NS
Answer
xtom.nl. 5 NS ns3.xtom.com.
xtom.nl. 5 NS ns1.xtom.com.
xtom.nl. 5 NS ns2.xtom.com.
xtom.nl. 5 NS ns4.xtom.com.
Authority
The response has no authority records.
Additional
ns1.xtom.com. 5 A 188.244.98.133
ns2.xtom.com. 5 A 188.244.99.133
ns3.xtom.com. 5 A 188.244.98.134
ns4.xtom.com. 5 A 188.244.99.134
ns1.xtom.com. 5 AAAA 2a0d:2900:a:0:0:0:98:133
ns2.xtom.com. 5 AAAA 2a0d:2900:a:0:0:0:99:133
ns3.xtom.com. 5 AAAA 2a0d:2900:a:0:0:0:98:134
ns4.xtom.com. 5 AAAA 2a0d:2900:a:0:0:0:99:134
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0