Caramel Apple Cake with Salted Caramel Buttercream

For the cake:

3¾ cups all-purpose flour

1 tablespoon baking powder

1½ teaspoon baking soda

2 teaspoon ground cinnamon

½ teaspoon salt

1½ cups packed brown sugar

¾ cup vegetable oil

¾ cup unsweetened applesauce, not chunky

¾ cup prepared caramel sauce

1 tablespoon vanilla extract

3 large eggs

1½ cups buttermilk

1 apple peeled, cored, and finely diced

For the frosting:

3 cups granulated sugar

1½ cups buttermilk

18 ounces butter, divided

1 teaspoon baking soda

1 to 1½ teaspoon fleur de sel, or other flaked salt (not table or Kosher salt)

2-3 cups powdered sugar

1 teaspoon vanilla extract

1 cup roughly chopped salted peanuts (optional)

12- to-18-inch long handled wooden spoon (round handle)

Cake: Preheat the oven to 325 degrees. Spray two 1½-quart (7x3-inch) casserole dishes* with nonstick cooking spray and line the bottom of each with parchment paper.

Combine flour, baking powder, baking soda, cinnamon, and salt, and whisk together. Set aside.

In the bowl of a large stand mixer, combine the brown sugar and oil, using the paddle attachment, mix together on medium speed until well-combined. Add applesauce, caramel sauce, and vanilla extract, mix until thoroughly combined. Add the eggs one at a time, beating well after each addition.

Add one-third of the dry ingredients and mix until most flour streaks are combined, but not all. Add half of the buttermilk and mix. Repeat, with flour as the last addition. Stop the mixer when there are just a few streaks of flour remaining. Remove bowl from mixer, add diced apples, and fold together by hand until thoroughly combined.

Divide the batter evenly between pans. Bake cakes at 325 degrees for about approximately 40 minutes, or until a toothpick, or skewer, inserted into the center comes out clean. Allow cakes to cool at room temperature, then when they're barely warm to the touch, invert onto cooling racks, ending with parchment side down, and allow to cool completely.

Remove parchment, and wrap cakes in plastic wrap. Place in the freezer for 30 minutes to firm. This step helps make frosting and assembling the cake easier.

Frosting: Combine the granulated sugar, buttermilk, 12 ounces of butter, and baking soda in a 6-quart pot. (Be sure to use a large enough pot as mixture will expand at least three times its size.) Place pan over medium-high heat, stirring until butter melts and sugar dissolves. Bring mixture a boil, stirring occasionally, until temperature registers 240 degrees Fahrenheit on a candy thermometer.

Once at 240 degrees, remove pan from the heat and carefully pour hot mixture into bowl of a large stand mixer fitted with a whisk attachment. Whisk on medium speed until caramel has slightly cooled and thickened, about 6 minutes. It might start to look a little grainy; that's okay.

Add the remaining 6 ounces of butter, 1 teaspoon salt, and vanilla extract: mix well. Add the powdered sugar in ½-cup increments, mixing on well after each addition. Once all the ingredients are added, whip on medium-high speed for about 10 seconds, until it's light and fluffy. Use immediately.

Assembling Cake: Once the cakes are firm, not completely frozen, remove from the freezer. Use a very long, sharp serrated knife, slice each in half horizontally. Carefully, slice the dome off one of the two cakes. This should leave three similar sized cake rounds, and one with a domed top.

Place one "bottom" cake on cake plate, or cardboard round. Spoon roughly 2/3 to ¾ cup of frosting in the center of the cake. Using an offset spatula, spread frosting to edges of cake. Repeat this process twice resulting in a three-layer apple-shaped cake topped with frosting.

Inserting wooden spoon: cut a slit into the center of the top two layers of the assembled cake. Gently press spoon into cake, being careful to not insert too far. Working with remaining cake round, dome side up, cut a ½-inch "X" into the center. With "X" carefully centered over spoon handle, gently lower onto cake.

Using serrated knife, sculpt top layer of cake to be rounded and resemble a caramel apple. If desired, you may also trim bottom layer as well.

The frosting is firm, so using either an offset spatula, or your hands, cover cake in frosting.

To finish, warm spatula with hot tap water, drying completely before touching cake, carefully smooth frosting. You will need to repeat the spatula heating process frequently.

If desired, press peanuts into bottom half of cake to resemble the peanuts on a caramel apple.

*If you don't need an apple-shaped cake, feel free to use two 9 x 2-inch round cake pans, or a 9 x13-inch pan instead. If using the latter, consider making a half recipe of frosting.

Serves 12-18