For the icing:
- 16 ounces caramel
- 1/2 cup hot water
- 1 cup butter, room temperature
- 1 cup confectioners’ sugar
For the cake:
- 2 cups + 2 tablespoons cake flour, sifted
- 1 teaspoon baking powder
- 3/4 teaspoon baking soda
- 1/2 teaspoon salt
- 1/2 cup unsalted butter, softened
- 1 cup sugar
- 1 teaspoon vanilla extract
- 2 large eggs, at room temperature
- 1 cup buttermilk
- Preheat the oven with a rack in the middle position to 350 degrees F.
- In a double boiler over low heat, heat the caramels and the hot water. Stir until smooth.
- In the bowl of a stand mixer fitted with a paddle attachment, mix the butter and sugar on low speed. Increase speed to medium, and slowly add the caramel mixture. Mix until thoroughly combined. Transfer to a medium bowl, and set aside. Clean mixer bowl and paddle.
- Butter an 8-inch square cake pan, and line with with parchment paper. Butter the parchment paper. Set aside.
- In a medium bowl, combine the cake flour, baking powder, baking soda and salt.
- Refit the paddle attachment in the stand mixer. Beat the butter and sugar on medium speed until fluffy. Beat in vanilla until well combined. Add eggs 1 at a time, beating well after each egg. Reduce the speed to low. Beat in buttermilk until just combined. Add flour in 3 batches. Allow each batch to combine before adding the next.
- Spread the batter evenly into the cake pan. Bake until golden or until a cake tester inserted into the center comes out clean, about 35 minutes.
- Allow the cake to cool in its pan for 10 minutes, then run an offset spatula around the edge of the pan. Invert the cake onto a cooling rack. Discard parchment, then allow to cool completely, about 1 hour.
- Pour the prepared caramel sauce over the entire cake, and serve.