01 -
Preheat the oven to 350°F (175°C) and grease an 8x8-inch baking pan.
02 -
In a microwave-safe bowl, melt the butter. Stir in sugar, eggs, and vanilla extract until well combined.
03 -
Add cocoa powder, flour, baking powder, and salt to the wet ingredients. Mix until fully incorporated.
04 -
Pour half of the brownie batter into the prepared pan, spreading evenly.
05 -
In a separate bowl, mix together pumpkin puree, egg yolk, sugar, cinnamon, and nutmeg.
06 -
Drop spoonfuls of the pumpkin mixture on top of the brownie batter and swirl with a knife or toothpick.
07 -
Pour the remaining brownie batter on top and swirl again if desired.
08 -
Bake for 25-30 minutes, or until a toothpick inserted comes out with moist crumbs. Let cool before cutting.