In a medium saucepan over medium heat, combine granulated sugar and water, stirring until dissolved. Allow the mixture to simmer until it turns a rich amber color, about 8-10 minutes.

Carefully stir in the unsalted butter and heavy cream until smooth. Remove from heat and let cool slightly before refrigerating to thicken.

Preheat your oven to 340ºF (170ºC). In a large mixing bowl, sift together flour, cornstarch, baking powder, and baking soda.

In another bowl, cream unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes. Gradually add in eggs, alternating with dry mixture, sour cream, vegetable oil, and vanilla extract.

Divide the batter into two greased and floured round pans. Bake for 20-23 minutes or until a toothpick inserted comes out clean. Let cakes cool in pans for 10 minutes before transferring to wire racks.

In a large bowl, beat the softened butter until fluffy and pale, about 5 minutes. Gradually add sifted powdered sugar until combined.

Stir in cooled salted caramel and a pinch of salt, beating until light and creamy. Adjust texture with additional cream if needed.

Place one cooled cake layer on a serving plate. Spread with buttercream, drizzle with caramel, and repeat with the second layer. Apply a crumb coat of buttercream and chill for 20-30 minutes.

Finish decorating the cake with remaining buttercream and a drizzle of caramel.

Slice the assembled cake into generous portions. Serve with whipped cream or a scoop of vanilla ice cream. Enjoy!