Preheat an oven to 350°F/175°C. Grease a 10-inch bundt pan with butter then coat with flour. Set aside.
In a large bowl, sift together the dry ingredients: flour, sugar, cocoa powder, baking soda, baking powder and salt. Set aside.
In a medium bowl, mix together eggs, oil, vanilla and buttermilk until combined. Mix in Nutella until combined. With a mixer on low speed, slowly add the wet mixture into the dry mixture. Then add hot coffee and stir to combine. Keep whisking until the batter is fully combined and smooth.
Scrape the batter into prepared pan. Bake for 45-55 minutes or until a toothpick inserted in the center comes out clean. If the top is browning too fast while baking, cover pan loosely with aluminum foil. Remove the cake from the oven and place it on a wire rack. Allow to cool completely. Then remove cake from pan, carefully inverting it onto a plate.