Preheat the oven to 350 degrees.
Grease two 8inch pans and line them with parchment paper.
In a medium mixing bowl mix together the eggs, buttermilk, oil, and vanilla.
In a large mixing bowl whisk together the flour, sugar, cocoa, baking soda and salt. Pour the wet ingredients into the dry ingredients and mix just until they are incorporated. Pour in the boiling water and stir until well combined.
Pour the batter into the two cake pans evenly. Reduce the oven to 300 degrees and bake the cakes for 30-35 minute or until a toothpick comes out clean from the center.
Let the cakes cool for 5 minutes then transferring the cakes to a cooling rack. Let them cool for an hour.
Slice the tops of the cakes just so they are nice and flat. Place one cake onto your serving platter.
Place the buttercream into a pastry bag that has a star tip inside. Pipe out a half inch layer of buttercream onto the first layer of cake. Sprinkle half of the pecans over the buttercream then drizzle with about 2 tablespoons of caramel sauce.
Place the second cake on top. Pipe another half inch layer of buttercream and sprinkle the remainder of pecans on top making sure to leave a half-inch border around the cake. Drizzle the caramel sauce over the top of the pecans. Pipe a border of buttercream around the top of the cake and one swirl right in the middle. You can add a whole pecan right in the middle of the cake to finish.