Preheat the oven to 350 degrees F. Butter and flour 3 8-inch cake pans.
In a medium bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder and salt.
In the bowl of a stand mixer fitted with the paddle attachment, combine the eggs, buttermilk, yogurt, melted chocolate, oil, and vanilla, and mix on medium speed for about 3-4 minutes.
*If your ingredients were cold, adding the chocolate may cause some lumps in the mixture, but this won't affect the finished product.
Turn the mixer speed down to low and add the dry ingredients in two batches, mixing until combined. Slowly add the coffee, scraping down the sides and bottom of the bowl, and mix until smooth and fully combined.
Distribute the cake batter evenly among the three pans. I like to use a scale for this, especially when doing a naked frosting style, so that the layers will be of equal size.
Bake layers for 30-35 minutes, or until a toothpick inserted in the center comes out clean. Cool in pans for at least 20 minutes before turning the layers out onto a cooling rack.
Frost the cake to a smooth finish. Slowly pour some caramel sauce over the top of the cake, spreading it to the edges with an offset spatula so that it drips down the sides.