Carrot Sheet Cake with Cream Cheese Sour Cream Frosting

We prefer to make this cake in a 13 x 9-inch pan, deeper than a sheet pan. The cake then has a denser texture that stands up to this rich frosting, a tangy contrast to the sweet cake.

8 tablespoons (1 stick) cool unsalted butter, cut into chunks, plus additional for greasing the pan

2 cups all-purpose fl our, plus additional for dusting the pan

1⁄2 cup cake fl our

11⁄2 teaspoons baking powder

11⁄2 teaspoons ground cinnamon

1⁄2 teaspoon baking soda

1⁄2 teaspoon grated nutmeg

1⁄2 teaspoon salt

3⁄4 cup packed dark brown sugar

3⁄4 cup granulated sugar

1⁄2 cup walnut oil

5 large eggs, at room temperature

3 cups grated carrots (through the large holes of a box grater or with the grating blade in a food processor)

2 tablespoons finely grated orange zest

1 cup finely chopped toasted pecans, walnuts, or pine nuts

Cream Cheese Sour Cream Frosting

• Position the rack in the center of the oven and preheat the oven to 350°F. Lightly butter and fl our a 13x9-inch baking pan, making sure all the corners and edges are evenly coated and tapping out any excess.
• Whisk both fl ours, the baking powder, cinnamon, baking soda, nutmeg, and salt in a medium bowl; set aside.
• Using an electric mixer at medium speed, beat the butter, sugars, and walnut oil in a large bowl until creamy and light, about 4 minutes.
• Beat in the eggs one at a time, making sure each is fully incorporated before adding the next. Beat in the grated carrots and orange zest until the batter itself is fairly smooth (although there will of course be threads of carrot and zest throughout).
• Turn off the beaters, add half the prepared flour mixture, and beat at low speed just until moistened. Add the remaining fl our mixture; beat just until evenly distributed.
• Scrape down the beaters and remove them. Use a rubber spatula to fold in the nuts, taking care to turn the batter thoroughly to check for any pockets of fl our or lumps. Pour and scrape into the prepared pan.
• Bake until lightly puffed and springy to the touch, until a toothpick or cake tester inserted into the cake’s center comes out with a few crumbs attached, about 55 minutes. Cool completely before icing.
• To cool: Set on a wire rack until room temperature, at least 11⁄2 hours, before topping with the Cream Cheese Sour Cream Frosting.
• To store: Do not ice. Lightly cover with plastic wrap and recake to come back to room temperature before icing.

Makes one 13 x 9-inch sheet cake