Preheat the oven to 350 degrees F.
Spray a 12-cup bundt pan with vegetable oil spray. In a small saucepan, melt chocolate over low heat, stirring constantly. Scrape the chocolate into a medium bowl and let cool slightly. Whisk in the oil and sugar until smooth, then whisk in the egg.
In a small bowl, whisk the flour, cocoa powder, baking powder, cayenne pepper, and salt. Add half of the dry ingredients to the chocolate mixture along with 1/2 cup of the coffee and 1/2 cup of the buttermilk; whisk until smooth. Add the remaining dry ingredients, coffee and buttermilk and whisk until smooth.
Pour the batter into the prepared pan and bake in the lower third of the oven for about 35 to 45 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumbs attached. Let the cake cool on a rack for 10 minutes, then turn it out and let cool completely.
Make the Ganache:
Place chocolate in a bowl. Heat cream in a small saucepan until simmering, and then pour over chocolate. Let stand for 2 minutes and stir. Add butter, liqueur, if using, vanilla extract, powdered sugar, cinnamon, cocoa powder, and salt until smooth. Let stand, stirring occasionally, until slightly thickened.
Once cake is cooled, place on a cake platter and drizzle with ganache. Garnish with fruit of your choice.