Carmelized Apple Skillet Cake

I'll never turn down a good apple tart / skillet cake. But my wife's apple cake still takes the cake, so to speak. This recipe comes from the Amateur Gourmet.

Caramelized-Apple Skillet Cake
from Karen DeMasco's "The Craft of Baking"

Ingredients:

• 1 cup sugar
• 8 tablespoons (1 stick) unsalted butter, very soft
• 2 tart baking apples, such as Mutsu or Granny Smith
• 3/4 teaspoon pure vanilla extract
• 2 large eggs, separated
• 3/4 cup plus 3 tablespoons unbleached all-purpose flour
• 3 tablespoons coarse yellow cornmeal or fine polenta
• 1 1/2 teaspoons baking powder
• 1/4 teaspoon kosher salt
• 1/3 cup whole milk
  

Preheat the oven to 350 F.

In an 8-inch ovenproof skillet, preferably cast iron, combine 1/4 cup of the sugar with 2 tablespoons water, stirring to make sure all of the sugar is damp.

Cook over high heat, stirring occasionally, until the sugar turns a golden brown caramel, about 2 minutes. Remove the pan from the heat and whisk in 2 tablespoons of the butter.

Peel, core, and using a mandoline or a sharp knife, cut the apples crosswise into 1/8-inch thick rings. Tightly shingle all of the apple rings over the caramel, starting around the outside of the skillet and working toward the center, overlapping the slices.

[Note from Adam: that step may've been where I messed up, I only had one apple. But would that have made the cake less likely to detach?]

In the bowl of an electric mixer fitted with the paddle attachment, combine the remaining 3/4 cup sugar, the remaining 6 tablespoons butter, and the vanilla. Beat on medium speed until light and fluffy, about 3 minutes. Mix in the egg yolks, one at a time.

In another bowl, whisk together the flour, cornmeal, baking powder, and salt. In three additions, add the flour mixture, alternating with the milk, to the butter mixture. Using a rubber spatula, scrape the batter into a large bowl.

Clean and dry the bowl of the electric mixer well. Add the egg whites and, using the whisk attachment on medium speed, beat to soft peaks, about 4 minutes. In three additions, fold the whites into the batter.

Spread the batter evenly over the apples in the skillet.

Bake, rotating the skillet halfway through, until the cake is golden brown and firm to the touch, 45 to 50 minutes. Place the skillet on a wire rack and let it cool just until the cake is warm, about 30 minutes. Then run a knife around the edge of the cake and invert it onto a plate. Serve warm or at room temperature.

The cake is best eaten the day it is baked but can be kept at room temperature, wrapped in plastic wrap, for up to 2 days.