No idea how I found this out, probably just from being on the BotW subreddit, but the specific timings are 23:30 - 00:00. This guarantees a crit effect from your meals (more duration, more hearts etc).
In my head it was informed in a loading screen or by an NPC but I can’t find anything online that confirms this, so guess I just came across a thread once!
I think 5 x Hearty Durians is 20 temporary hearts normally but under a blood moon I got 24 temporary hearts in one recipie.
I really dislike the cooking mechanics, so I try to avoid it as much as possible. It means I also avoid fights, though, or else try to get really good at dodging. But 20 temp hearts? That’s incredible. I didn’t even know such a big buff was possible.