Makes:1 (8-inch) layer cake, or 8 to 10 servings
Making a layer cake using zucchini may sound weird, but the end result is really a kindred spirit to carrot cake. The batter is mixed by hand with cinnamon and nutmeg, then grated zucchini is folded in; cake flour gives it a light texture and fine crumb. The frosting is a riff on cream cheese frosting but uses a buttercream base with some yogurt mixed in for tang. Then, the whole cake is coated with toasted pecans for a stunning and unique spice cake that’ll help you use up zucchini from the garden.
What to buy: For this recipe, use bleached cake flour such as Softasilk, for a tender cake that will rise high and evenly. Do not use unbleached cake flour, which yields denser results.
Game plan: If you have a food processor, use it to chop the pecans. It’ll be faster and you’ll have more uniform pieces.
3 cups bleached cake flour, such as Softasilk, plus more as needed
1 1/2 teaspoonsbaking powder
1 1/2 teaspoonsground cinnamon
1 teaspoonbaking soda
1/2 teaspoon freshly ground nutmeg
1/2 teaspoon fine salt
4 large eggs, at room temperature
1 cup packed dark brown sugar
1 cup granulated sugar
1 cupvegetable oil
2 teaspoonsvanilla extract
14 ounceszucchini (about 3 to 4 medium zucchini), ends trimmed and grated on the large holes of a box grater (about 3 cups)
For the buttercream frosting and nut filling:
4 sticks (1 pound) unsalted butter, at room temperature
1 3/4 cupspowdered sugar
1 tablespoonvanilla extract
1/4 teaspoon fine salt
1 cup plain whole-milk Greek yogurt, at room temperature
2 cupspecans (about 8 ounces), toasted and finely chopped
For the cake:
Heat the oven to 350°F and arrange a rack in the middle. Cut out 2 (8-inch) rounds of parchment paper; set aside. Coat 2 (8-inch) cake pans with butter, place the rounds in the pans, and coat the parchment with more butter. Coat the pans and parchment with flour and tap out any excess; set aside.
Place the measured flour, baking powder, cinnamon, baking soda, nutmeg, and salt in a large bowl and whisk to aerate and break up any lumps; set aside.
Combine the eggs, sugars, oil, and vanilla in a second large bowl and whisk until the eggs are broken up and the mixture is thoroughly combined. Using a rubber spatula, fold in the flour mixture until just combined. Fold in the zucchini until evenly mixed.
Divide the batter evenly between the prepared pans. Bake side by side on the middle rack, rotating from one side to the other halfway through the cooking time, until a cake tester or toothpick inserted in the center comes out clean, about 40 to 45 minutes.
Transfer the cakes to a wire rack to cool slightly, about 15 minutes. Run a knife around the perimeter of each and turn the cakes out onto the rack to cool completely.
Using a serrated knife, trim a very thin layer from the top of each cake, just enough to even out the surface; set aside.
For the buttercream frosting and nut filling:
Place the butter and sugar in the bowl of a stand mixer fitted with a paddle attachment and beat on low speed until the sugar is incorporated, about 30 seconds.
Increase the speed to medium high and beat until the mixture is light in color, about 3 minutes. Stop the mixer and scrape down the sides of the bowl and the paddle.
Return the mixer to medium-high speed and add the vanilla and salt. Add the yogurt 1/3 cup at a time until all of it has been added, then continue mixing until the frosting is evenly combined and light in texture, about 3 minutes. (It’s very important that the yogurt is at room temperature, or the frosting will seize and form clumps.)
For the filling, transfer 1 1/4 cups of the frosting to a medium bowl and mix in 2/3 cup of the pecans; set aside.
To frost the cake, place a layer on an upside-down cake pan. Evenly spread all of the nut filling over the top of the layer, then place the second cake layer on top, cut-side down. (This way you have a really smooth, even surface to frost.) Using an offset spatula or long, thin knife, spread the remaining frosting evenly over the top and sides of the cake.
Using your hands, gently press the remaining 1 1/3 cups pecans into the frosting around the sides of the cake. (It’s helpful to do this over a baking sheet to catch any falling pecans.) Carefully slide 2 long, flat spatulas under the cake from opposite directions, lift the cake off the cake pan, and transfer it to a serving plate.
If you don’t plan to eat the cake within 4 hours, tent it with plastic wrap and refrigerate it for up to 3 days. To serve, let the cake sit at room temperature for about 45 minutes to take the chill off before slicing.