Do web redirects ever use nginx?

Hi — My client has a website with a mysterious and stubborn 301 redirect off of its root URL. I am 90% sure that this is happening at the web server level, but I want to rule out Cloudflare as a culprit. If you look at the attached screenshot, you’ll see that the 301 response includes HTTP headers from Cloudflare. However, the response body looks to have been generated/rendered by nginx. So my question is: is there any scenario in which a redirect triggered by Cloudflare would involve nginx in this way? Or is this sufficient proof that it’s the web server that’s in control? To note: we just have the domain’s DNS records and nameservers on Cloudflare. No proxy. No redirect or transform rules anywhere that I can identify. curl -v indicates that a connection to the server IP is being made, SSL certificate negotiated, etc., which again seems to strongly indicate local machine rather than network behavior. Am I wrong?