Pumpkin Swirl Brownies

I made these pumpkin brownies last week, and they are one of my favorite things I have ever made. The cayenne pepper is a great addition. The recipe is from Martha Stewart. Delicious! 

8 tablespoons (1 stick) unsalted butter, plus more for pan

6 ounces bittersweet chocolate, chopped (I used Ghirardelli)

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 solid-packed pumpkin

1/4 cup vegetable oil

1 teaspoon ground cinnamon

1/4 teaspoon ground nutmeg

1/2 cup chopped hazelnuts 

Preheat oven to 350 degrees. Butter a 9-inch square baking pan or dish. Line bottom of pan with parchment paper; butter lining.

Melt chocolate and butter in a heatproof bowl set over a pan of simmering water, stirring occasionally until smooth.

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.

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.