One you are familiar with, if possible. Django, Rails, or maybe Elixir+Phoenix if you absolutely need something modern.
However, that's only because I still have the luxury of time. If I had a gun to my head and a finite number of hours to code an app, then I'd go with vanilla Rails. If I was given a few weeks to study a new framework, I'd go with Elixir/Phoenix, but only because I spent a few days trying it around and while I'm not particularly fluent with it yet, I like its design and speed a lot more than Rails.
I think this is why we perfect our craft. We have to be able to code fast or code pretty, depending on the circumstances.