Preheat your oven to 350°F (175°C). Grease two 9-inch round cake pans and line the bottoms with parchment paper. This makes it easier to remove the cakes later.

In a large bowl, whisk together the flour, granulated sugar, brown sugar, cocoa powder, baking powder, baking soda, salt, and cinnamon (if using).

In a separate bowl, mix the pumpkin puree, eggs, vegetable oil, buttermilk, and vanilla extract until smooth. Slowly add the hot water, stirring gently until combined.

Gradually pour the wet ingredients into the dry ingredients, mixing until just combined. Be careful not to overmix—this ensures a light, tender cake.

Divide the batter evenly between the prepared pans. Bake for 35–40 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Using an electric mixer, beat the cream cheese and butter until smooth and creamy. Gradually add the powdered sugar and cocoa powder, beating until fluffy. Mix in the vanilla extract and milk, one tablespoon at a time, until the frosting reaches your desired consistency.

Place one cake layer on a serving plate and spread an even layer of frosting on top. Add the second layer and frost the top and sides. If you want, decorate with chocolate shavings, a dusting of cocoa powder, or even a drizzle of caramel sauce.