Apex domains cannot have CNAME records.
Question and response
Question
dig vodafone.com. NS
Answer
vodafone.com. 5 NS ns3.vodafone.com.
vodafone.com. 5 NS ns5.vodafone.com.
vodafone.com. 5 NS ns1.vodafone.com.
Authority
The response has no authority records.
Additional
ns1.vodafone.com. 5 A 47.73.65.141
ns3.vodafone.com. 5 A 47.73.20.173
ns5.vodafone.com. 5 A 47.73.31.237
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0