Apex domains cannot have CNAME records.
Question and response
Question
dig teamviewer.com. NS
Answer
teamviewer.com. 5 NS tv-ns4.teamviewer.com.
teamviewer.com. 5 NS tv-ns1.teamviewer.com.
teamviewer.com. 5 NS tv-ns2.teamviewer.com.
teamviewer.com. 5 NS tv-ns3.teamviewer.com.
teamviewer.com. 5 NS tv-ns5.teamviewer.com.
Authority
The response has no authority records.
Additional
tv-ns1.teamviewer.com. 5 A 217.146.18.1
tv-ns2.teamviewer.com. 5 A 188.172.248.1
tv-ns3.teamviewer.com. 5 A 213.227.160.1
tv-ns4.teamviewer.com. 5 A 213.227.191.1
tv-ns5.teamviewer.com. 5 A 185.81.208.1
tv-ns1.teamviewer.com. 5 AAAA 2a00:11c0:aa1:0:0:0:0:1
tv-ns2.teamviewer.com. 5 AAAA 2a05:8900:aa1:0:0:0:0:1
tv-ns3.teamviewer.com. 5 AAAA 2605:380:aa1:0:0:0:0:1
tv-ns4.teamviewer.com. 5 AAAA 2803:ad80:aa1:0:0:0:0:1
tv-ns5.teamviewer.com. 5 AAAA 2a00:11c0:1010:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0