Apex domains cannot have CNAME records.
Question and response
Question
dig edge2.salesforce.com. NS
Answer
edge2.salesforce.com. 4 NS ns01.salesforce-dns.com.
edge2.salesforce.com. 4 NS ns03.salesforce-dns.com.
edge2.salesforce.com. 4 NS dns2.p02.nsone.net.
edge2.salesforce.com. 4 NS dns1.p02.nsone.net.
edge2.salesforce.com. 4 NS dns4.p02.nsone.net.
edge2.salesforce.com. 4 NS dns3.p02.nsone.net.
edge2.salesforce.com. 4 NS ns02.salesforce-dns.com.
edge2.salesforce.com. 4 NS ns04.salesforce-dns.com.
Authority
The response has no authority records.
Additional
dns1.p02.nsone.net. 1 A 198.51.44.2
dns2.p02.nsone.net. 1 A 198.51.45.2
dns3.p02.nsone.net. 1 A 198.51.44.66
dns4.p02.nsone.net. 1 A 198.51.45.66
ns01.salesforce-dns.com. 1 A 45.54.69.1
ns02.salesforce-dns.com. 1 A 45.54.69.65
ns03.salesforce-dns.com. 1 A 45.54.69.129
ns04.salesforce-dns.com. 1 A 45.54.69.193
dns1.p02.nsone.net. 1 AAAA 2620:4d:4000:6259:7:2:0:1
dns2.p02.nsone.net. 1 AAAA 2a00:edc0:6259:7:2:0:0:2
dns3.p02.nsone.net. 1 AAAA 2620:4d:4000:6259:7:2:0:3
dns4.p02.nsone.net. 1 AAAA 2a00:edc0:6259:7:2:0:0:4
ns01.salesforce-dns.com. 1 AAAA 2607:f740:e629:0:0:0:0:1
ns02.salesforce-dns.com. 1 AAAA 2607:f740:e629:4:0:0:0:1
ns03.salesforce-dns.com. 1 AAAA 2607:f740:e629:8:0:0:0:1
ns04.salesforce-dns.com. 1 AAAA 2607:f740:e629:c:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0