3 1/2 cups Cup4Cup flour
1 tablespoon baking powder
3/4 teaspoon baking soda
1 teaspoon kosher salt
2 sticks (1/2 pound) unsalted butter at room temperature
2 cups granulated sugar
4 large eggs, left at room temperature for 30 minutes
2 teaspoons vanilla extract
2 cups sour cream
1/2 teaspoon orange extract
Zest of 2 large oranges
5 tablespoons cocoa powder
1/2 cup chocolate chips
1/4 cup orange juice
1. Preheat oven to 350°F. Butter and flour two 1.5-pound loaf pans.
2. Sift together Cup4Cup flour, baking powder, baking soda and salt and set aside.
3. Beat together butter and sugar in a large bowl with an electric mixer at medium speed, until pale and fluffy, about 3 minutes. Add eggs one at a time, beating well after each addition, then beat in vanilla. Reduce speed to low, add half of flour mixture, and mix until just blended. Add sour cream, mixing until just combined, then add remaining flour mixture and mix until smooth. Batter will be very thick.
4. Divide the batter evenly into two bowls. In one bowl, add the orange zest and orange extract and stir to combine. In the other bowl add the orange juice, sifted cocoa powder, and chocolate chips and stir to combine. Batters should be very thick.
5. First evenly spread the orange batter into the bottom of the pan. Next, add the chocolate batter on top of the orange to cover. No swirling is necessary, although you can swirl the batters together if you like using a small offset spatula.
6. Bake until cake is springy to the touch and a wooden pick inserted in the center comes out clean, about 45 minutes to 1 hour.
7. Remove from oven and cool cake in the pan for 30 minutes. Remove cakes from the pans, place onto a cooling rack and cool completely.