Breton Apple Cake

On Thanksgiving morning, I ran our annual Turkey Trot.  I haven't exactly been training, or doing any sort of exercise for that matter, so it took me just about an hour to finish the 5 mile run.  Luckily, my 17 year old cousin isn't much of a runner, so we ran together the whole way.  It was fun to watch all the cool costumes that people wore as they ran past me.  But, you know you are running slow when 2 men run past you, each carrying a full-sized canoe over their head...yeah, that happened!  Anyway, when I got home, I started to put things together to bring to my mom's house for dinner.  My sister-in-law was making a pumpkin pie, so to have a non-pumpkin option, I chose to make this cake, which I found on Baking Bites.  Though I was quite full after dinner, I did manage to try a tiny slice before leaving for my in-law's house for after-dinner drinks.  I ate it plain, but I'm sure it would have been equally delicious sprinkled with powdered sugar or next to a scoop of vanilla ice cream!

1/2 cup Butter, room temperature
3/4 cup Sugar
3 Eggs, separated
2 teaspoons Vanilla Extract
1/4 cup Plain Yogurt
1 1/2 cups Flour
1 teaspoon Baking Powder
1/4 teaspoon Salt
2 Apples, peeled and thinly sliced

In a large bowl, cream together the butter and sugar until light and fluffy.  Beat in the egg yolks, followed by the vanilla and yogurt.  Sift in the flour, baking powder, and salt and mix just until all ingredients are well combined and no streaks of flour remain.  The batter will be quite thick.  In a medium bowl, beat together the egg whites to stiff peaks.  Stir about half of the egg whites into the cake batter (using an electric mixer on low) to lighten the batter, then gently mix in the remaining egg whites.  Fold in the apple slices.  Pour the batter into a lightly greased 9-inch springform pan (I just used a 9-inch cake pan).  Bake at 350 degrees for 45-50 minutes, until the cake is golden brown and a toothpick inserted near the center comes out clean.  Cool for at least 40 minutes before serving.  Serves 8.