Wheat-free chestnut cake - help!

[cdnyc]

Hi. I am a new member, and am having trouble with a cake I wanted to make for my son's upcoming birthday party. He has a friend who is allergic to wheat, so I wanted to make a cake she could eat, and found a recipe online for a cake made entirely with chestnut flour. I don't bake often, usually only in my bread machine, and this is my first time using chestnut flour. Well, the mixing seemed to go fine, the batter was really thick, and then it started baking and when I checked looked great - the cake had risen a lot and smelled divine. The recipe said to cover loosely with aluminum foil for the last 10 mins of baking, so I did. When I covered the cake it was still high and looked great. When I removed it from the oven 10 minutes later, it had fallen to half the size and was really dark around the edges. It tastes good in the middle, but the sides and bottom are bitter and taste rather burnt. So what did I do wrong? Is it just that I cooked it too long? Why do I need to cover for the last 10 minutes? (Because obviously I couldn't see what was going on with the foil in place.) And then how can I know it's ready to be covered?
Further info that may be useful: My spring form pan is nonstick and kinda dark, so did that play a part? Also I have a vintage oven from circa 1940 that is gas and is definitely NOT perfect, though last I checked the temperature was correct.

[cheesecake man]

It would be better if you use a light colored, aluminum/stainless steel, pan for your cakes. The dark pan will reduce the baking time needed. With our cheesecakes it will take about 10 minutes of baking time off the time needed if we use our dark colored pans vs aluminum colored pans, based on an hour of baking time. Sounds like your oven is ok since you recently checked the temp. Hope this helps! Happy b'day to your son!

[LieR]

mmm, for me the collapse almost half size was a lot.
may be you have add some Xanthan Gum or Guar Gum, because it's replace gluten. and it will help to maintain the body of the cake. let's start with 1% from total cheestnut flour you use.
Hope it's can help your cake, and Happy Birthday to your Son.....
10 minute cover by aluminium at last usually meant to give time for the cake to adjust temperature, give more time to cake to be baked, also to avoid loosing moist too much. but if that reason made a trouble, try to not do that and see the result