My Website's Domain has been compromised. Someone has somehow synced his domain with mine

I have a website https://emailhow.net/ and today I got to know that someone is running exactly the same website as mine on https://arturrr.com/. Initially, I thought that someone has copied my website using any website copier tool but upon investigation, I found that somehow arturrr.com has been synced to my domain emailhow.net and whatever changes I am making to my website are being reflected on another website in real-time. I tried taking down my website from Cloudflare, changed the hosting, restored the backup from Feb 2021, and even deleted all the websites file and just created an HTML file printing hello. No matter what I am doing on the website is reflecting on the other domain. I don't know how someone is doing this and how can I get rid of it. Please help if anyone has any clue on it.