Preheat oven to 350 degrees F.
Butter a 9-inch square baking pan or dish
.Line bottom of pan with parchment paper.
Melt chocolate and butter in a heatproof bowl set over a pan of simmering water, stirring occasionally until smooth (or do what Mom did and just zap it in the microwave, turned out fine!)
.Whisk together flour, baking powder, cayenne, and salt in a large bowl and then add sugar, eggs, and vanilla.
Use an electric mixer fitted with the paddle attachment; beat until fluffy and well combined, 3 to 5 minutes.
Beat in flour mixture.• Divide batter between two medium bowls (about 2 cups per bowl).
Stir chocolate mixture into one bowl. In other bowl, stir in pumpkin, oil, cinnamon, and nutmeg.
Transfer half of chocolate batter to prepared pan smoothing top with a rubber spatula.
Top with half of pumpkin batter. Repeat to make one more chocolate layer and one more pumpkin layer.
Work quickly so batters don't set.
• With a small spatula or a table knife, gently swirl the two batters to create a marbled effect. Sprinkle with nuts.• Bake until set, 40 to 45 minutes. Let cool in pan on a wire rack.
Cut into 16 squares
