I made a baked apple recipe with a crumb stuffing (recipe here), and then accidentally left one of them out in the dish overnight. Is it safe to eat? (Checked stilltasty.com, my reference for such things, and couldn't find it)
While not an exact match, Still Tasty indicates up to 2 days for an apple pie at room temperature; one would expect the baked apple to have similar properties.
So yes, I would expect eating your baked apple the next day should be fine.
I would not hold them much longer than that, though, as the cooking helps bring out moisture which will foster growth of molds over time.