Preheat the oven to 350°F.
Mix together the flour, baking powder, and salt in a bowl.
In another bowl, combine melted butter, sugar, and vanilla. Mix in eggs one at a time. Gradually add the flour mixture, then divide the batter into two bowls.
Mix cocoa powder and chocolate chips into one bowl of batter. In the other bowl, mix in pumpkin purée, cinnamon, cloves, and nutmeg. Grease an 8-inch square baking pan.
Spread half of the chocolate batter into the pan, followed by half of the pumpkin batter. Add dollops of each remaining batter, then swirl with a knife.
Bake for 45 minutes or until a toothpick comes out clean.