Pick a famous or well-known piece of writing and write about how you would have written it instead.
Note, the prompt isn’t to rewrite the known work, but to write about how you would have approached writing it and why. Maybe it’s a book by a writer of another gender and you think they missed some points, or, maybe it was a piece of futurism at the time but now it needs updating, maybe the writing begs for a sequel. Whatever issues you take with the work, now’s your chance to dig in, to keep going, or to revisit.