The original recipe had the baking times reversed. The onions should caramelize, which takes 15-20 minutes, at least. Most baking apples will turn to mush, if they are left to steam for 15 minutes. When reversed, the recipe is quite good. My sons (2 and 7) were delighted to find the apples were sour, and the onions were sweet (I used yellow onions and Granny Smith apples. Though this would go great with German food (it's very similar to several German dishes), I've served it with Moroccan Chicken and similar dishes that are heavy on the spices (not necessarily the heat), when you want something sweet and sour to give you a break from the complex flavors.
I used Chef VP's tip and switched the cooking times--longer on the onions, less on the apples. I also added a couple pieces of cooked chopped bacon the last few minutes for some additional flavor. Turned out well!
I didn't love this recipe as much as I thought I would, but my parents sure did. I used Pink Lady apples; I'm not sure if another variety would be better in this recipe (maybe that was what I didn't like). I used butter, not bacon grease.