Apex domains cannot have CNAME records.
Question and response
Question
dig mx.waaf.net. NS
Answer
mx.waaf.net. 5 NS dns.wn-dns.de.
mx.waaf.net. 5 NS ns3.waaf.net.
mx.waaf.net. 5 NS ns2.waaf.net.
mx.waaf.net. 5 NS ns1.waaf.net.
Authority
The response has no authority records.
Additional
dns.wn-dns.de. 5 A 46.101.245.225
ns1.waaf.net. 5 A 35.156.243.225
ns2.waaf.net. 5 A 54.36.113.70
dns.wn-dns.de. 5 AAAA 2a03:b0c0:3:d0:0:0:28:b001
ns2.waaf.net. 5 AAAA 2001:41d0:701:1000:0:0:0:b99
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0