Preheat your oven to 350°F (175°C). Grease and flour three 9-inch round cake pans.

In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until well mixed.

Add the buttermilk, vegetable oil, eggs, and vanilla extract to the dry ingredients. Mix until well combined.

Gradually pour in the hot water, stirring until the batter is silky and smooth.

Divide the batter evenly among the prepared pans.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool in the pans for about 10 minutes before transferring them to a wire rack to cool completely.

In a saucepan, heat the sugar over medium heat until it melts and turns amber. Add the butter and stir until melted.

Gradually pour in the heavy cream while stirring constantly. Remove from heat and stir in the vanilla extract and salt. Let cool.

In a microwave-safe bowl, heat the chocolate chips and heavy cream in 30-second intervals, stirring until completely smooth.

Place one cake layer on a serving plate. Spread a layer of caramel sauce, sprinkle with chopped pecans, and drizzle with chocolate ganache.

Repeat with the remaining cake layers.

Frost the top and sides of the cake with the remaining caramel sauce and ganache. Decorate with pecan halves.

Chill for at least 30 minutes before serving.