Caramel Apple Cake
2 cups sugar
3/4 cup unsalted butter, room temperature
5 egg whites, lightly beaten
2 3/4 cups all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup buttermilk
2 teaspoons vanilla
SPICED APPLE FILLING
3 Granny Smith apple, peeled thinly sliced
1/4 cup sugar
1 teaspoon ground cinnamon
juice of 1/2 lemon
3 tablespoons apple juice or water
2 cups sugar
1 cup unsalted butter, cubed
1/2 cup buttermilk
1 teaspoon baking soda
1 teaspoon fresh lemon juice
chopped dry roasted peanuts (optional)
FOR CAKE: Preheat oven to 350 degrees with rack in the center. Grease two 9" round cake pans with nonstick spray. Line with rounds of parchment paper, spray again and dust with flour.
Cream together sugar and butter in a large mixing bowl until light. Gradually add eggs whites, beating until well blended. Sift flour, baking soda and salt.
Combine buttermilk and vanilla. Add 1/3 of the flour mixture to the butter mixture; mix just until blended. Add 1/2 the buttermilk mixture and blend just to incorporate. Scrape the bowl, add half the remaining flour, and blend. Scrape bowl again, then add the remaining buttermilk. Fold in the last of the flour by hand, making sure no flour is at the bottom.
Divide batter among prepared pans, about 2 1/2 cups per pan. Bake for 40-45 minutes or until a toothpick inserted in the center comes out clean. Cool cakes on a rack for 5 minutes, turn out onto a cooling rack, and peel off the parchment Cool before filling and frosting.
Saute apples in butter over medium-high heat with sugar, cinnamon, lemon juice and salt. Cook until fruit begins to caramelize around the edges, about 15 minutes. Stir periodically, but not so much that the apples don't caramelize. Deglaze with juice, stir, and cook another 2-3 minutes, or until liquid is nearly (but not totally) evaporated. Cool apples before filling cake. Do not stir too much. Prolonged contact with the pan helps caramelize the apples.
Boil all ingredients (except the peanuts) in a tall, heavy saucepan over medium heat, stirring until butter melts and mixture starts to boil. Cook, stirring occasionally, until icing caramelizes, about 8 minutes. Remove from heat and cool 5 minutes. It will continue to caramelize off heat.
Beat icing with a hand mixer until lighter incolor and thick, about 5 minutes. It should be liquid enough to drip down the sides of the cake. This icing foams up a lot and can bubble over easily.
Once the icing is beaten, you have to put the cake together quickly. If you wait, the icing will stiffen and make for problematic spreading. However, if it does thicken a bit, just thin it out with a teaspoon or two of buttermilk of milk. Achieving the ideal consistency is tricky, but the perfect icing will flow from a spoon in a thick stream when poured.
To assemble, start by spreading about one cup of icing over one of the cake layers. Push the icing to the edges but don't force it to drip over. It will happen naturally when the apple filling and the second cake layer are positioned on top.
Now, carefully arrange the apple filling on the icing. Get the apples as close to the edge as possible without spilling over. If there's any juice left in the saute pan, drizzle it over the apples-it'll soak into the top cake layer.