Make the Cake:

1. Preheat oven to 350°F (175°C). Grease and line three 8-inch round cake pans with parchment paper.
2. In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
3. In a large bowl, beat butter and sugar until light and fluffy (about 2-3 minutes).
4. Add eggs one at a time, beating well after each addition. Stir in vanilla extract.
5. Alternate adding the dry ingredients and buttermilk, beginning and ending with dry ingredients. Mix until just combined.
6. Divide batter evenly between the cake pans and bake for 25-30 minutes, or until a toothpick inserted comes out clean.
7. Let cakes cool in pans for 10 minutes, then transfer to a wire rack to cool completely.

Make the Salted Caramel Sauce:

1. In a saucepan over medium heat, melt the sugar, stirring constantly until it turns a deep amber color.
2. Carefully add butter, stirring until melted. Slowly pour in heavy cream, stirring continuously.
3. Remove from heat and stir in sea salt. Let cool to room temperature.

Make the Butterscotch Frosting:

1. Beat butter until creamy. Gradually add powdered sugar, mixing until smooth.
2. Add butterscotch sauce, vanilla extract, and salt. Beat until fluffy.
3. Add heavy cream if needed for a spreadable consistency.

Assemble the Cake:

1. Place one cake layer on a plate. Spread with butterscotch frosting and drizzle with salted caramel sauce.
2. Repeat with the second layer. Add the final cake layer and frost the entire cake.
3. Drizzle extra salted caramel sauce over the top and sprinkle with flaky sea salt.
4. Optional: Garnish with butterscotch chips for extra flavor.