Web server that grabs data from a URL, transforms it and returns to user

I'm trying to make a web server that will respond to requests from clients by grabbing data from another URL (not hosted by me), transforming and zipping that data, then returning that to the client as a download. I've got a ubuntu web server set up with nginx and python installed, but I've also been reading comments that imply that I need to use flask? I would rather keep everything as simple as possible, so would this sort of thing be possible without it? i.e. just getting nginx to call a python task which does the rest? This is new territory for me so I was just looking for some advice on where to start. Thanks!