If I would have a Tor hidden service connect to a clearnet CDN(such as cloudflare), would the request made be the Tor exit node's IP or the server's IP?
Connections to Tor hidden services do not involve exit nodes. Both user and hidden service build circuits to the rendezvous point. If the hidden service were configured to simply redirect to a clearnet CDN, the CDN would see the server's clearnet IP address. The server could instead redirect through a separate Tor circuit, and in that case the CDN would see a Tor exit IP address. But the added latency might offset benefit from the CDN.