Preheat your oven to 350°F. Grease and flour two 9-inch cake pans. Beat the butter and sugar until light and fluffy. Add eggs one at a time, mixing well after each. Stir in vanilla extract.
In a separate bowl, whisk flour, baking powder, and salt. Gradually add to the butter mixture, alternating with buttermilk, until smooth. Divide the batter evenly between the prepared pans.
Bake for 30–35 minutes or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
In a saucepan over medium heat, melt sugar until golden brown. Carefully stir in heavy cream and butter, whisking constantly. Cook for 5 minutes until smooth and thickened. Remove from heat and add vanilla extract. Let it cool slightly before frosting.
Spread a layer of caramel frosting between the cake layers. Coat the top and sides with the remaining frosting. Let it set for 15 minutes before slicing. Enjoy with Peanut Butter Cup Brownies for a decadent treat!