Making Cake Gluten Free

This is one of the cakes to make my mother famous (at least among her acquaintances). We have one old friend who requests this cake whenever she comes to visit. And this was the groom's cake John chose for our wedding. It also became one of the first recipes to establish me as a great baker. John was sad to think he'd never be able to eat this again, but I was too nervous to modify it, until last year, when I had a somewhat successful attempt. This year, after more cake successes, I tried again, and was very happy with the results. I still have to modify temperature and use regular butter instead of unsalted, but now I can happily add this back to my repertoire.
So, I'm not sure that I'll take the time to post the long, complicated recipe for this particular Lemon Marzipan cake, but will revel in the success of making it gluten free, and discuss the things I have learned about adjusting cake recipes.
1) Choose your recipe wisely. If it's a really light, really fluffy cake whose recipe requires a lot of flour: don't try it. Dense cakes, especially chocolate ones, modify perfectly. Also, the best yellow cake I've modified came from a recipe using cake flour, prized for its lower amount of gluten and therefore easier to modify. Also, cakes that require more eggs (like 3), or that require dividing the egg and folding the whipped whites into the batter hold their shape better, so do well with gluten free flours.
2) Make sure the cake has a great frosting or something to help out the flavor. Somehow, rice flour mixes don't make for the tastiest cakes, but something like this, where the texture of the cake is what is needed with the ultra flavorful lemon buttercream and marzipan, works perfectly. I also find that the yellow cakes I've made taste marvelous with great chocolate frosting.
3) I have found a curious combination of flours that seems to work very well with cakes and sweet breads: 2/3 of the recipe as Featherlight flour, and the remaining 1/3 GF mix. I think I was introduced to this by the Eating Gluten Free girls, but I'm not certain. I've been using it for a little while adjusting recipes, and I've been happy with it every time.
4) If in doubt, add an egg. If the recipe doesn't already call for an insane amount of eggs, I add one. Somehow, it makes things hold together better and come out nicer.
5) Add xanthan gum, about 1/2 teaspoon per cup of flour used, although typically you don't need more than 1 teaspoon per recipe.
6) Cakes need to be cooked thoroughly to hold their shape, which is a problem with gluten-free flours. Holding their shape that is, not being cooked thoroughly. Because of this fact, I sometimes favor a lower temperature for a longer time period so it cooks slowly and evenly. Maybe even try it in a water bath.

For this cake, I added an egg, an extra 1/2 teaspoon baking powder, and an extra egg, using the same amount of flour called for but adjusting the mixes as I described above. It worked really well. I wouldn't necessarily recommend the cake on its own, but the texture was pretty perfect (barring the outside that was overcooked because I cooked it at too high of a temperature for my dark pan) and it's not supposed to stand on its own but meld with the other flavors.

Enough of my idle prattle, these are some of the things I've learned about baking gluten free cakes. The thing that stands out the most for me though is, it's possible. I've made good special occasion cakes gluten free, and that's something I didn't think possible before.