I'm sorry Mirj. This one didn't work out too well. I ended up baking it way longer than called for to get the sweet potatoes where I get get a fork into them, and by that time, the apples had gotten too mushy (and I did use the Cortlands). I did try tasting it, the apples had a flavor of lemon (even with the cider in the pan), and were a bit tart. I tried sprinkling with some cinnamon and nutmeg and drizzling honey over it all, and that did help tone that down some, and bring out some flavor. I think maybe the apples should be cut larger (in wedges) and those sweet potatoes cut thin, and do prepare for some honey or brown sugar on the apples at least. I think maybe that could help this recipe work.
You need to slice the sweet potatoes thinner than the apples, I also added brown sugar, a touch of nutmeg and cinnamon. When slicing the apple, have a bowl with cool water and a few drops of lemon juice handy, put slices in the water until ready to layer. This keeps them clear of browning, and avoids the overly lemon taste that other reviewers complained about.
This is VERY similar to a recipe by the same name in Jane Brody's Good Food Book. I have made it for years and have always had a good result. The differences between Ms. Brody's recipe and this one I believe caused the problems mentioned in the previous comment. I will submit the one I am familiar with.