If I understand correctly you removed your website from Cloudflare after having configured Cloudflare DNS; now you’re trying to visit your website and you see this error message.
Based on the info you provided it looks like your DNS resolver is still providing the Cloudflare CDN IP addresses when looking up your website, instead of returning NXDOMAIN or providing the new record you may have configured on a new provider.
The changes caused by your domain removal should propagate after some time. If you switched to a new DNS provider, make sure you configure the correct nameservers on your registrar. Has the situation changed since when you posted this?