Obviously, Apple is responsible for the creation of iOS itself and its design guidelines. No pressure! We responded by doing our homework: we immersed ourselves in iOS interaction design, particularly for iPad, to figure out what was the "Apple" way to do things.
The initial goal was to make the app feel congruous with the level of quality expected from an Apple-designed app, but not necessarily to look like the Apple brand. However, after we explored a few different visual directions, we got feedback that it was veering too far off from the Apple brand to be an Apple-affiliated app.
So, we dialed it way back and went with subtle branding choices instead, like the dark blue as the primary callout color. We were aiming for a utilitarian and professional, but still modern and sleek look and feel.
The app went live in India to positive feedback, especially with regard to the speed of the end-to-end transactions. (Unfortunately there is no public link, since it is not a consumer-facing app.)
On a personal level, I learned how to work effectively with a team of designers — collaborative skills as well as the practical things like how to share Sketch files and label artboards for minimal confusion.