Step 1: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line with parchment paper.
Step 2: In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Step 3: Add the buttermilk, vegetable oil, eggs, and vanilla extract to the dry ingredients. Beat with an electric mixer on medium speed for 2 minutes until well combined.
Step 4: Carefully stir in the hot coffee (or hot water) until the batter is smooth. The batter will be thin.
Step 5: Divide the batter evenly between the prepared cake pans. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with moist crumbs.
Step 6: Let the cakes cool in the pans for 10-15 minutes before inverting them onto a wire rack to cool completely.
Step 7: To make the Salted Caramel Sauce: In a medium saucepan, combine the sugar and water. Cook over medium-high heat without stirring, gently swirling the pan occasionally, until the mixture turns a deep amber color (about 8-10 minutes).
Step 8: Remove from heat and carefully pour in the warmed heavy cream (it will bubble vigorously). Whisk until smooth. Add the cubed butter and sea salt, whisking until the butter is fully melted and incorporated. Let cool slightly.
Step 9: Once the cakes are completely cool, place one layer on a serving plate. Spread a thin layer of salted caramel sauce on top. Place the second cake layer on top.
Step 10: Drizzle generously with more salted caramel sauce, allowing some to drip down the sides. Arrange the fresh raspberries on top of the cake.
Step 11: Optionally, dust with powdered sugar before serving.