Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large bowl, whisk together flour, baking powder, baking soda, and salt.

In a separate bowl, cream together sugar and butter until light and fluffy.

Beat in eggs one at a time, then stir in vanilla.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.

Pour batter evenly into the prepared pans.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Let cool in pans for 10 minutes before inverting onto a wire rack to cool completely.

In a saucepan, melt sugar over medium heat, stirring constantly until it becomes a golden caramel.

Remove from heat and whisk in butter and heavy cream until smooth.

Stir in sea salt and let cool slightly.

In a bowl, beat together powdered sugar and softened butter until creamy.

Gradually add the cooled caramel to the powdered sugar mixture and beat until smooth and fluffy.

Level the cake layers if needed.

Place one layer on a serving plate and spread with a generous amount of frosting.

Top with the second layer and frost the top and sides of the cake.

Drizzle with extra caramel, if desired, and serve.