Combine the flour, sugar, cocoa powder, baking soda, baking powder, salt, and cinnamon in a bowl. Whisk together to fully combine the ingredients and break up any lumps.
Add in eggs, oil, and buttermilk. Stir until almost combined. There should still be some clumps of flour throughout.
Then stir in the cup of boiling water. Gently, stir in the water. Be careful! Some water may splash out on you while stirring!
Line a cupcake dish with liners and fill about 2/3’s of the way full.
Bake for about 18-20 minutes, until a toothpick inserted comes out clean.
Frosting:
Add Nutella, frosting, and vanilla extract to a bowl
Whip on high speed for about 2 minutes.
Place a closed star tip into a piping bag and add in the frosting.
I think this works best by holding the piping back more vertical versus at a 45-degree angle. Squeeze enough pressure to make a star in the center of the cupcake. Then using the same amount of pressure continue to pull the frosting around the center part swirling upwards to make a mountain.