Recursive Update

Hi, how do you update the recursive servers for Technitium? If you remove specific forwarders. I noticed that when I didn't have a 3rd-party forwarder, a website was being blocked, but as soon as I added back my 3rd-party NextDNS, the URL was not blocked and was free to access. So my question is, how do I update Technitium when there is no forwarder present, so it knows what URLs are valid? Thanks