Apex domains cannot have CNAME records.
Question and response
Question
dig squarespace.com. NS
Answer
squarespace.com. 2 NS dns4.p06.nsone.net.
squarespace.com. 2 NS dns1.p06.nsone.net.
squarespace.com. 2 NS ns02.squarespacedns.com.
squarespace.com. 2 NS ns04.squarespacedns.com.
squarespace.com. 2 NS dns2.p06.nsone.net.
squarespace.com. 2 NS dns3.p06.nsone.net.
squarespace.com. 2 NS ns01.squarespacedns.com.
squarespace.com. 2 NS ns03.squarespacedns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0