This cake is amazing with just about any type of fruit.
1/2 cup unsalted butter
1/4 cup light brown sugar
1 pound apples, cored & sliced into thin wedges
1 1/2 cups flour
2 teaspoons baking powder
1/4 teaspoon salt
1 cup sugar
2 yolks
1 teaspoon plus a few drops vanilla
1/2 cup milk
2 egg whites
1/4 teaspoon cream of tartar
1 cup heavy cream
1 tablespoon confectioners sugar
Butter a 9-inch cake pan. Melt the 4 tablespoons of the butter and brown sugar in the bottom of the cake pan. Place the apple slices, arranged into circles, in the cake pan on top of the melted butter and sugar.
Preheat oven to 350°F. Mix the flour, baking powder and salt together. Cream the remaining 1/4 cup butter and sugar together in a bowl. Add the yolks to the creamed mixture, one at a time, beating well after each addition. Add 1 teaspoon of the vanilla. Mix well. Add the milk alternately with the dry ingredients to the above batter, folding well after each addition. Beat the egg whites to soft peaks. Add the cream of tartar and continue to beat until the peaks hold their shape. Fold the whites into the cake batter. Spread the batter over the fruit and bake until a toothpick inserted into the center of the cake comes out clean, about 55 to 60 minutes.
Remove from the oven and run a small knife around the edges of the cake. Let cook 15 minutes. Invert the cake onto a serving platter and let it sit another 5 minutes with the pan on the top. Remove the pan. In the meantime, whip the cream to soft peaks. Flavor with the remaining few drops of vanilla and the confectioners sugar.
Serve slices of cake with softly whipped cream.