Pumpkin-Swirl Brownies

From marthastewart.com

• Ready In: 1 hr 20 mins
• Serves: 16
• Yields: 16 brownies

Ingredients

• 8  tablespoons unsalted butter
• 6  ounces bittersweet chocolate
• 2  cups all-purpose flour
• 1  teaspoon baking powder
• 1⁄4 teaspoon cayenne pepper
• 1⁄2 teaspoon salt
• 1 3⁄4 cups sugar
• 4  large eggs
• 1  tablespoon pure vanilla extract
• 1 1⁄4 cups canned pumpkin
• 1⁄4 cup  vegetable oil
• 1  teaspoon ground cinnamon
• 1⁄4 teaspoon ground nutmeg
• 1⁄2 cup walnuts

Directions

1. Preheat oven to 350 degrees. Butter a 9-inch square baking pan or dish. Line bottom of pan with parchment paper; butter lining.
2. Melt chocolate and butter in a heatproof bowl set over a pan of simmering water, stirring occasionally until smooth.
3. Whisk together flour, baking powder, cayenne, and salt in a large bowl; set aside. Put sugar, eggs, and vanilla in the bowl of an electric mixer fitted with the paddle attachment; beat until fluffy and well combined, 3 to 5 minutes. Beat in flour mixture.
4. 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.
5. With a small spatula or a table knife, gently swirl the two batters to create a marbled effect. Sprinkle with nuts.
6. Bake until set, 40 to 45 minutes. Let cool in pan on a wire rack. Cut into 16 squares.