Ingredients
Nonstick cooking spray or oil, for the pan
2 cups/260 grams all-purpose flour
1 ½ teaspoons ground cinnamon
1 teaspoon ground ginger
½ teaspoon ground cardamom
1 teaspoon baking soda
1 teaspoon baking powder
1 teaspoon fine salt
1 cup/200 grams granulated sugar
1 lemon
3/4 cup/150 grams vegetable oil
½ cup/120 grams sour cream
2 large eggs
2 1/2 cups/250 grams finely grated carrots (from 3 carrots; see Tip)
3/4 cup/75 grams chopped walnuts, plus more for topping
2 (8-ounce/226-gram) blocks cream cheese, preferably Philadelphia (see Tip), softened
2 cups/230 grams powdered sugar
1/4 cup/60 grams sour cream
1/8 teaspoon fine salt, plus more to taste
Directions
1
Make the cake: Heat the oven to 350 degrees. Lightly coat a half-sheet pan (13 by 17 inches) with nonstick cooking spray and line the bottom and two long sides with parchment paper.
2
Whisk the flour, cinnamon, ginger, cardamom, baking soda, baking powder and salt in a medium bowl.
3
Pour the sugar into a large bowl and zest the lemon directly over it. Gently rub the zest into the sugar; save the lemon for the frosting. Add the oil, sour cream and eggs to the sugar and whisk until smooth and pale yellow, 1 to 2 minutes. Add the carrots and stir until evenly distributed.
4
Add the flour in thirds, gently stirring after each addition to make sure there are no lumps. Add the walnuts and stir gently to disperse. Pour the batter into the prepared pan and spread evenly. It will be a very shallow layer of batter.
5
Bake until a toothpick inserted in the center comes out clean, about 20 minutes. Cool completely in the pan on a rack.
6
The cake should have released from the short sides. If not, run a knife along those edges. Cut the cake into three even rectangles, each about 13 by 5 1/2 inches. (If you’d like very neat edges, slide the cake onto a cutting board first, then trim all the edges before cutting into 3 rectangles.)
7
Make the frosting: Beat the cream cheese with an electric mixer or by hand using a wooden spoon or stiff spatula until very smooth. (It’s hard to get lumps out once other ingredients are added.) Add the powdered sugar and beat until creamy and smooth.
8
Squeeze 1 teaspoon juice from the reserved lemon and add, along with the sour cream and salt. Stir until smooth, then taste and season with more lemon juice and salt if needed.
9
Assemble the cake: Place one layer bottom side up on your serving plate. (A clean cutting board works, too.) Spread a third of the frosting (about 1 cup per layer) evenly to the edges, then top with another cake layer and half of the remaining frosting. Set the final cake layer on top, bottom side up, and spread the remaining frosting over it. You can leave the edges unfrosted or, if you want, coat them with frosting squishing out from the sides. Sprinkle walnuts on top.
10
Refrigerate the cake for at least 30 minutes for the frosting to stiffen and for the cake to set. The cake can be chilled for up to 3 days before serving. Let sit at room temperature for about 15 minutes before serving.
Notes
Use the small holes on a box grater or other grater to get small shreds of carrots.
Philadelphia cream cheese has a pronounced savory tang. If you’re using another brand of cream cheese, taste the frosting after it’s been beaten, and add more lemon juice and salt to make it flavorful.