Buttermilk Caramel Cake

Preheat oven to 350°F. Coat three 8-inch round cake pans with nonstick cooking spray; line bottoms with parchment. In a medium bowl stir together flour, baking powder, 1/2 teaspoon baking soda, and 1 teaspoon kosher salt.

In the bowl of a stand mixer beat 1 cup butter on medium-high until fluffy and a pale yellow (1 minute). Add 1 1/2 cups granulated sugar; beat another 3 minutes, scraping bowl as needed. Add eggs, one at a time, beating well after each addition. Add vanilla and beat well. Scrape down sides of bowl. Reduce mixer speed to lowest setting; add flour mixture and 1 1/4 cups buttermilk alternately, beginning and ending with flour. Divide batter evenly among pans. Bake about 25 minutes or until a cake tester comes out clean. Transfer to cooling racks and let cool in the pans 10 minutes. Invert layers onto cooling racks, remove paper, and let cool completely. If the layers are rounded on top, trim flat.

Place a rack inside a sheet pan lined with parchment. Place a cardboard cake round covered in foil on rack. Invert one cake layer onto round.

For frosting: In a 6-quart heavy-bottom pot combine the brown sugar with the remaining 1 1/2 cups granulated sugar, 1 1/2 cups buttermilk, 1 1/2 cups butter, and 1 1/2 teaspoons baking soda. Cook over medium, stirring frequently, until mixture comes to a boil. Watch carefully; once it comes to a boil, the mixture will foam up. Lower heat as necessary to prevent foaming over. Cook, uncovered, to 235°F degrees on a candy thermometer (30 to 35 minutes). Adjust heat as necessary to maintain a moderate, steady boil across surface. Remove from heat. Using a wooden spoon, beat until creamy, thick, and spreadable (8 to 10 minutes). Mixture will become lighter in color and start to lose its gloss.

Working quickly before frosting starts to harden, spread some frosting on top of the cake layer on rack. Top it with a second cake layer and ice it. Place remaining layer on top. Pour frosting over top and allow it to drip down the sides, spreading evenly. If frosting starts to harden, warm over low. Spoon any frosting that pools at the base back over sides. For a smooth finish, dip spatula in hot water and go over the top and sides of cake. Serves 12.