In a medium saucepan over low heat, combine granulated sugar and water, stirring until the sugar dissolves. Increase heat to medium and cook until mixture turns golden brown, about 8-10 minutes.

Remove from heat, stir in butter, then whisk in heavy cream gradually. Allow to cool and add a pinch of salt.

Preheat oven to 340ºF (170ºC). Sift together flour, baking powder, baking soda.

In a mixing bowl, beat butter and sugar until fluffy. Incorporate eggs, sour cream, and vanilla. Mix in dry ingredients and oil alternately.

Grease two 9-inch round cake pans and distribute batter evenly. Bake for 20-23 minutes until toothpick inserted comes out clean.

Cool layers in pans for 10 minutes, then transfer to wire rack to cool completely.

Beat softened butter until creamy. Gradually add powdered sugar and cooled salted caramel. Mix until fluffy.

Once cooled, place one layer on plate, spread buttercream, drizzle salted caramel, place second layer on top.

Apply a thin buttercream crumb coat, refrigerate for 30 minutes to set.

Remove cake from refrigerator and apply remaining buttercream for a smooth finish. Drizzle with extra salted caramel and sprinkle sea salt on top.