Preheat oven to 350°F (175°C). Butter and flour three 8-inch round pans, lining the bottoms with parchment paper.
Whisk together dry ingredients in a large bowl.
Whisk together wet ingredients in another bowl. Add to dry ingredients, mixing gently. Add hot coffee, mix until smooth (batter will be thin).
Divide batter into prepared pans. Tap to release air bubbles.
Bake for 22-25 minutes, until a toothpick comes out with a few moist crumbs. Let cool for 10 minutes in pans, then remove and cool completely.
Make the Salted Caramel:
In a saucepan, heat sugar and water over medium-high heat until it turns amber (8-10 minutes). Carefully add room temperature cream and whisk until smooth.
Stir in butter, salt, and vanilla. Let cool for 15-20 minutes before using. Reserve ¼ cup for topping.
Prepare the Chocolate Frosting:
Beat softened butter until creamy. Gradually add sifted powdered sugar and cocoa powder.
Add heavy cream, vanilla, and salt. Beat until light and fluffy (2-3 minutes).
Assemble the Cake:
Place one cake layer on a plate, frost, and add salted caramel. Repeat with the second layer.
Add the final layer of cake and apply a crumb coat. Chill for 15-20 minutes.
Apply the remaining frosting and drizzle with reserved caramel. Garnish with flaky sea salt and optional chocolate shavings.
Refrigerate and Serve:
Chill for 30 minutes to set the frosting. Let cake come to room temperature before serving.
Notes
Make Ahead: Cake layers and caramel can be made a day in advance and stored in the fridge.
Substitutions: Use gluten-free flour for a gluten-free option, and dairy-free substitutes for vegan versions.
Serving Tips: Let the cake come to room temperature for the best flavor and texture.