Point of view switch in flashback.
(New York )
Question: My story is in first person POV, but I need to flashback to a scene in another character's perspective. Rather than have this character tell in exposition, I'd prefer to write the flashback event in "real time" in the other character's POV. First, would this be acceptable? Second, might you have an example of how to transition into the second POV?
You are certainly free to use a flashback. You can find plenty of successful novels where it happens.
Some readers find the technique a little jarring, which is why it may be better to find a different way to convey the information. But a flashback is often the best option if you don't want your main character to know about this event, for purposes of dramatic irony.
Most often, you will see a scene like this as a prologue or epilogue. Putting it in the middle of a novel is more problematic because you will be interrupting the flow of the main character's narrative. If it is information that the main character must find out, some alternatives include putting it in a journal entry or letter that the main character finds, or having it appear in a dream (if your main character happens to be psychic). Fantasy writers have so many options here.
Bare minimum, you should probably give this scene its own chapter. Any other clues that can let the reader know you've changed points of view would be helpful. Sometimes an obvious clue, such as naming the chapter something like "Kesha's Story," or starting the chapter with a date (to show the time shift) works well, even if it's not terribly subtle. It would also help if the second character expresses himself in a different style of writing.
Incidentally, there's nothing wrong with putting this chapter in past tense, or third person, or even italics (if it's short). These are also ways of signalling to the reader that a different voice has taken over.