Is it possible to send traffic through the VPN tunnel to the VPN gateway itself?

I have a WAN interface X and a web server Y behind NAT, that is traffic to X:443 is being forwarded to Y:443. Web server is accessible from the internet without any problems.

Then I have a site-to-site VPN connection where X happens to be a remote gateway. I set up DNAT in the VPN tunnel so that VPN traffic to X:443 goes to Y:443 and made sure the firewall allows the traffic to go through.

Still, no packets, neither DROPPED nor FORWARDED reach X:443 from the VPN tunnel.

Is it technically possible to send traffic through the VPN tunnel to the VPN gateway itself?

I don’t seem to be able to make it work. My web server external IP is X but X is also a VPN gateway and the server is not accessible through VPN tunnel. I wonder if I am missing something…yet, mysteriously, it works from my other L2TP VPN connection where X is also the gateway. Site-to-site VPN is IPSec. Any thoughts?