"You don't have permission to access / on this server." Problem

Hello! Im having trouble with my SSL Certificate.

Domain: poetic-creponne-7244fa.netlify.app
Custom Domain: Cittadinidesign.com

Whenever I visit I get a 403 Error saying: “You don’t have permission to access / on this server.”
I also see an error in my dashboard that says: SniCertificate::CertificateNonvalidError: Unable to verify challenge for www.cittadinidesign.com

Neither cittadinidesign.com nor www.cittadinidesign.com are served by Netlify

$ dig cittadinidesign.com
cittadinidesign.com.	4489	IN	A	66.96.162.130
$ dig www.cittadinidesign.com
www.cittadinidesign.com. 4502	IN	A	66.96.162.130

The certificate is that of bizland.com

$ curl -svo /dev/null 2>&1 https://cittadinidesign.com | egrep 'Server certificate' -A5
* Server certificate:
*  subject: CN=*.bizland.com.
*  start date: Aug  2 00:00:00 2023 GMT
*  expire date: Sep  1 23:59:59 2024 GMT
*  subjectAltName does not match cittadinidesign.com
* SSL: no alternative certificate subject name matches target host name 'cittadinidesign.com'

I suggest checking the DNS which is currently domain.com

$ dig cittadinidesign.com NS
cittadinidesign.com.	4502	IN	NS	ns2.domain.com.
cittadinidesign.com.	4502	IN	NS	ns1.domain.com.

Edit:
I see you have tried to add the domain to Netlify DNS. However, you have not removed the aforementioned name servers

$ whois cittadinidesign.com | egrep '^Name Server'
Name Server: ns2.domain.com
Name Server: ns1.domain.com
Name Server: dns1.p09.nsone.net
Name Server: dns2.p09.nsone.net
Name Server: dns3.p09.nsone.net
Name Server: dns4.p09.nsone.net