For the cake
2 1/8 cups (215 g) drained grated zucchini (See Recipe Notes)
2 cups (280 g) all purpose gluten free flour (I used Better Batter but you can use any of my favorite blends (click the link))
1 teaspoon xanthan gum (omit if your blend already contains it)
1 1/4 teaspoons baking powder
1/4 teaspoon baking soda
1/2 teaspoon kosher salt
1/2 cup (100 g) granulated sugar
1/2 cup (108 g) packed light brown sugar
8 tablespoons (112 g) unsalted butter, melted and cooled
2 eggs (100 g, weighed out of shell) at room temperature, beaten
2 teaspoons pure vanilla extract
1/2 cup (4 fluid ounces) milk (any kind), at room temperature
For the frosting
8 ounces cream cheese, at room temperature
2 tablespoons (28 g) unsalted butter, at room temperature
1 teaspoon pure vanilla extract
1/8 teaspoon kosher salt
1 1/2 to 2 cups (173 to 230 g) confectioners’ sugar
For the zucchini
I began with one medium-large fresh zucchini that weighed about about 400 grams, whole. You’ll shred it in a classic-sized box grater, place it in tea towels or a mesh nut milk bag, and squeeze out as much liquid as possible. What remains should be a bit more than 215 grams shredded, drained zucchini.
Preheat your oven to 325°F. Line a 9-inch square baking dish and set it aside.
Prepare the zucchini by grating it on a standard size box grater, and wring out as much moisture as you can using a tea towel or mesh nut milk bag. Measure out 215 grams as drained, and set the zucchini aside.
In a large bowl, place the flour blend, xanthan gum, baking powder, baking soda, salt, and granulated sugar, and whisk to combine well. Add the brown sugar and 215 grams of grated and prepared zucchini. Mix to combine, breaking all the lumps in the brown sugar, and any clumps in the grated zucchini.
Add the melted butter, beaten eggs, vanilla, and milk, and mix to combine. The batter will be thick but relatively soft. Transfer the batter to the prepared pan, and smooth into an even layer with a wet silicone or offset spatula.
Place the pan in the center of the preheated oven and bake for about 32 minutes, or until the cake springs back when pressed gently in the center. It should also be very lightly brown on top.
Remove the cake from the oven and allow it to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
While the cake is cooling, making the frosting. In a large bowl with a hand mixer or the bowl of a stand mixer fitted with the paddle attachment, place the cream cheese, butter, vanilla, and salt, and beat on medium-high speed until light and fluffy (about 3 minutes).
Add 1 1/2 cups (173 g) confectioners’ sugar, and beat until smooth (another or 2 minutes). I prefer this frosting to be soft and fluffy, but you can beat in up to another 1/2 cup confectioners’ sugar to reach your preferred consistency. The more confectioners’ sugar you use, then thicker the frosting will be.
Spread the frosting on top of the cooled cake, and slice it with a sharp knife into 9 or 12 pieces. You can also slice the cake bare and frost individual pieces.
If you don’t plan to serve the whole cake at once, slice the cake bare and wrap any individual unfrosted pieces tightly in freezer-safe wrap before freezing. Defrost at room temperature and frost before serving.