Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking pan. Melt the butter and mix with sugar in a large bowl. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract. In a separate bowl, combine flour, cocoa powder, and salt. Gradually add the dry ingredients to the wet mixture, stirring until combined.

In a medium bowl, beat the softened cream cheese until smooth. Add pumpkin puree, sugar, pumpkin pie spice, egg, and vanilla extract. Mix until well combined and creamy.

Spread the brownie batter evenly in the prepared pan. Pour the pumpkin cheesecake mixture on top, reserving a small amount. Use a knife to swirl the reserved cheesecake mixture into the batter, creating a marbled effect.

Bake in the preheated oven for 45-50 minutes, or until a toothpick inserted into the center comes out clean. Let the bars cool completely in the pan before slicing.

Once completely cooled, cut the bars into squares. Serve them as is, or with a dusting of powdered sugar or a drizzle of caramel sauce.

Place any leftovers in an airtight container and store in the refrigerator for up to 5 days. For longer storage, wrap the bars individually and freeze for up to 3 months.