caramel cake recipe

2 1/2 cups all-purpose flour - 2 teaspoons baking powder - 1/2 teaspoon baking soda - 1/2 teaspoon salt - 1 cup unsalted butter, softened - 1 1/2 cups granulated sugar - 4 large eggs - 2 teaspoons vanilla extract - 1 cup whole milk **For the Caramel Frosting:** - 1 cup unsalted butter - 2 cups packed brown sugar - 1/2 cup heavy cream - 1/4 teaspoon salt - 2 cups powdered sugar, sifted - 1 teaspoon vanilla extract