In a medium saucepan, combine granulated sugar and water over medium heat, stirring until sugar dissolves. Allow to boil until a rich amber color, about 8-10 minutes. Add butter and heavy cream in stages, stirring until smooth. Mix in salt and let cool.

Preheat oven to 340°F (170°C) and grease two 9-inch round cake pans. In a large mixing bowl, cream butter and granulated sugar until fluffy. Add eggs one at a time, incorporating each fully. Gradually mix in sour cream and vanilla. Fold dry ingredients into wet in two parts to ensure a smooth batter.

Pour batter into prepared pans, smoothing tops. Bake for 20-23 minutes until a toothpick inserted comes out clean. Allow cakes to cool in pans for 10 minutes before transferring to wire rack.

Let cake layers cool completely for about 30-45 minutes. Level tops of cakes if necessary.

In a large mixing bowl, beat unsalted butter until light and fluffy. Gradually add powdered sugar, mix on low until incorporated, then add vanilla and salted caramel, beating until smooth. Adjust consistency with more cream if needed.

Begin by placing one cake layer on a serving platter. Spread a layer of buttercream, followed by a drizzle of salted caramel. Place the second cake layer on top and gently press down. Apply a thin crumb coat of buttercream around the cake, chill for about 20 minutes.

Once chilled, frost the top and sides of the cake with remaining buttercream. Drizzle more salted caramel on top and sprinkle sea salt if desired. Serve the Salted Caramel Cake and enjoy!