Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour three 9-inch round cake pans and set aside.
Make the Chocolate Cake: In a large mixing bowl, sift together the flour, cocoa powder, granulated sugar, baking powder, baking soda, and salt. In another mixing bowl, whisk together the eggs, buttermilk, hot water, vegetable oil, and vanilla extract until well combined. Gradually add the wet ingredients to the dry ingredients, mixing until smooth and well combined. Divide the batter evenly between the prepared cake pans.
Bake the Cake: Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center of the cakes comes out clean. Remove from the oven and let the cakes cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.
Prepare the Caramel Frosting: In a saucepan over medium heat, melt the butter. Stir in the brown sugar, heavy cream, and salt. Bring the mixture to a boil, then reduce the heat to low and simmer for 2 minutes, stirring constantly. Remove the saucepan from the heat and let the caramel sauce cool for 5 minutes. Gradually whisk in the powdered sugar until smooth and well combined.
Assemble the Cake: Place one layer of the chocolate cake on a serving plate or cake stand. Spread a layer of caramel frosting over the top of the cake layer. Repeat with the remaining cake layers and frosting, stacking them on top of each other.
Make the Chocolate Ganache: In a small saucepan, heat the heavy cream until it just begins to simmer. Remove from the heat and pour it over the semisweet chocolate chips in a heatproof bowl. Let it sit for 2-3 minutes, then stir until smooth and glossy.
Decorate the Cake: Pour the chocolate ganache over the top of the assembled cake, allowing it to drip down the sides. Sprinkle the chopped pecans over the top of the cake. If desired, drizzle additional caramel sauce over the top for extra sweetness.
Chill and Serve: Place the Turtle Caramel Cake in the refrigerator for at least 30 minutes to allow the frosting and ganache to set. Once chilled, slice and serve, savoring each decadent bite of this indulgent dessert.