How to remap command and ctrl keys in an app

So, I've looked a the docs, and searched for 'remap' and 'binding', but I can't figure out if this is possible. In 1 app, I'd like to swap the command and ctrl keys. How can I do this?

BTT is not the best app for such things. I don't think this is possible. You could, for example, press and release ⌃ when you press and release ⌘. But ⌘ would also be activated. So you would press and release ⌘ and ⌃ at the same time … I think.