Preheat the oven to 350ºF. Line a 9x9 baking dish with foil and lightly coat with cooking spray.
Place the butter, chocolate, and espresso powder into a small saucepan and melt over low heat while stirring constantly until smooth and fully melted.
In a medium mixing bowl whisk the flour, baking powder, and salt together until well combined.
In the bowl of an electric mixer (or using a handheld mixer) beat the sugar, eggs, and vanilla extract together for 3 to 5 minutes, or until fluffy. Add the flour mixture and continue to mix until smooth and well combined.
Divide the batter between two medium bowls (about 2 cups in each bowl). Mix the chocolate mixture into the first bowl and set aside. In the second bowl whisk in the pumpkin, oil, and pumpkin pie spice until smooth.
Pour half of the chocolate mixture into the prepared baking dish and use a spatula to smooth and spread out. Top with half of the pumpkin mixture and carefully spread it out with a spatula as well. Repeat with the remaining chocolate mixture and pumpkin mixture.
Using a butter knife place it into the batter and gently swirl it all around the pan to create a marble effect. Work quickly so the layers don't set.
Bake for 40 to 45 minutes and let cool on a wire rack before slicing.