- Preheat oven to 175°C (350°F). Grease and flour a 9-inch round cake pan. 
- In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, cinnamon, cayenne, and salt. 
- In another bowl, beat the eggs with granulated sugar and brown sugar until light and fluffy. Add oil, buttermilk, and vanilla extract. Mix well. 
- Gradually add the dry mixture into the wet mixture, stirring gently until combined. 
- Slowly pour in the hot coffee and mix until smooth. Batter will be thin. 
- Pour the batter into the prepared pan and bake for 30–35 minutes or until a toothpick comes out clean. 
- Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. 
- (Optional) Top with chocolate ganache or whipped cream with cinnamon.