Prepare the Oven and Pans: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

Mix the Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.

Prepare the Batter: In a large mixing bowl, beat the softened butter and sugar together until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract. Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk. Mix until just combined.

Swirl in the Caramel: Pour half of the batter into each prepared cake pan. Drizzle half of the caramel sauce over the batter in each pan. Use a knife to swirl the caramel into the batter.

Bake the Cakes: Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Make the Frosting: In a large bowl, beat the softened butter until creamy. Gradually add the powdered sugar, mixing well. Add the heavy cream and vanilla extract, continue beating until smooth and fluffy.

Assemble the Cake: Place one cake layer on a serving plate. Spread a layer of frosting on top. Place the second cake layer on top and spread frosting over the top and sides of the cake. Optional: drizzle additional caramel sauce on top for decoration.