Chocolate Zucchini Cake with Buttercream Frosting

This chocolate zucchini cake with buttercream frosting is rich and decadent, as all chocolate cakes should be. It’s a great way to use up a summer abundance of zucchini and it’s perfect for snacking, birthdays, or when you’ve made all the zucchini bread you can eat.

A square of chocolate zucchini cake with buttercream frosting on a square of parchment with a fork standing up in the center of the cake.

Adapted from Amanda Rettke | Homestead Recipes | William Morrow Cookbooks, 2022

Amazingly rich and decadent, this cake is what all chocolate cakes should strive to be, and it’s so easy to make. No one will notice the zucchini in the cake, but they’ll be happy it’s there as soon as they take a bite and see how moist this cake is! I have paired it with chocolate buttercream, but truthfully, this cake is fantastic all on its own!–Amanda Rettke

Chocolate Zucchini Cake with Buttercream Frosting FAQs

Can I use any variety of zucchini?

Absolutely. Zucchini come in a number of shades and sizes: green, nearly black, golden – and all have similar tastes and textures. You can use any type of zucchini in this recipe. You can also swap yellow summer squash for the zucchini in this, and most other recipes.

Can this cake be made gluten-free?

Yes, simply substitute your favorite gluten-free flour 1:1 for the all-purpose flour, and remember that the substitution may alter the texture of your final results, but your cake will still be tasty.

Can zucchini cake be frozen?

Sure can. After baking, cool the cake completely, wrap it in several layers of plastic, and freeze it for up to 3 months. Frost the cake after thawing, when you are ready to serve.

Chocolate Zucchini Cake with Buttercream Frosting

A square of chocolate zucchini cake with buttercream frosting on a square of parchment with a fork standing up in the center of the cake.
You can enjoy this rich and indulgent chocolate zucchini cake with or without the buttercream frosting. Either way, it's excellent.

Prep 25 mins
Cook 50 mins
Total 2 hrs 15 mins
Dessert
American
15 servings
704 kcal
5 / 9 votes
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Ingredients 

For the chocolate zucchini cake

  • Nonstick spray
  • 2 cups granulated sugar
  • 4 large eggs at room temperature
  • 1 1/2 cups mild vegetable oil
  • 1 teaspoon vanilla extract
  • 2 cups all-purpose flour
  • 3/4 cup unsweetened cocoa powder
  • 2 teaspoons baking soda
  • 1 teaspoon baking powder
  • 3 cups (from 2 or 3 medium zucchini) grated zucchini undrained

For the chocolate buttercream frosting

  • 3 sticks (12 oz) unsalted butter at room temperature
  • 4 cups confectioners’ sugar
  • 3/4 cup unsweetened cocoa powder
  • 2 teaspoons vanilla extract
  • Pinch of table salt
  • 4 tablespoons heavy whipping cream

Directions
 

Make the chocolate zucchini cake

  • Preheat the oven to 350°F (175°C). Coat a 9- by 13-inch (23- by 33-cm) baking dish with nonstick spray.
  • In a medium bowl, use a spatula to stir together the sugar, eggs, oil, and vanilla. Add the flour, cocoa powder, baking soda, and baking powder and mix well. Fold in the zucchini until evenly distributed. Pour the mixture into the prepared baking dish.
  • Bake until a toothpick inserted in the center comes out with a few crumbs but no wet batter clinging to it, 35 to 50 minutes.
  • Let the cake cool to room temperature. Then spread the frosting on the cake, slice, and serve.

Make the chocolate buttercream frosting

  • In the bowl of a stand mixer fitted with the whisk attachment or in a large bowl using a handheld whisk, whisk the butter and confectioners’ sugar on medium-high speed until very pale and fluffy, about 5 minutes. Stop at least once to scrape the bowl.
  • With the mixer off, add the cocoa powder, vanilla, and salt. Turn the mixer on low and blend for about 30 seconds.
  • With the mixer running, add the heavy cream, a tablespoon at a time. When all the cream has been added and the mixture is mostly combined, remove the bowl from the mixer and scrape down the sides with a rubber spatula.
  • Turn the mixer to medium-high and mix until the frosting is light, fluffy, and shiny, 3 to 5 minutes.
  • Store in an airtight container in the refrigerator for 3 to 5 days.
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Show Nutrition

Serving: 1portionCalories: 704kcal (35%)Carbohydrates: 78g (26%)Protein: 6g (12%)Fat: 44g (68%)Saturated Fat: 17g (106%)Polyunsaturated Fat: 14gMonounsaturated Fat: 11gTrans Fat: 1gCholesterol: 103mg (34%)Sodium: 177mg (8%)Potassium: 308mg (9%)Fiber: 4g (17%)Sugar: 59g (66%)Vitamin A: 774IU (15%)Vitamin C: 7mg (8%)Calcium: 48mg (5%)Iron: 2mg (11%)

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Recipe Testers’ Reviews

Despite its popularity, I have never made bread or a cake with grated zucchini.

A square of chocolate zucchini cake with buttercream frosting on a china plate with a fork on the side.

As my first experience with this method, this chocolate zucchini cake recipe was a complete delight for a couple of reasons. First, the recipe is super simple to prepare as all the ingredients are assembled in one bowl. Second, it is a great way to add veggies to a baked good since the grated zucchini completely disappears during the baking process leaving you with a very moist and fudgy cake.

I made the chocolate buttercream frosting, but this cake is delicious by itself or served with a scoop of ice cream. A cream cheese frosting would also pair well with this cake.

The cake will serve a large number (at least 15) but freezes well and can be held in the freezer for a month or two. I would freeze the cake unfrosted and the buttercream separately (also very freezable!) in small portions so that the servings can be used as needed.

While I‘m not a huge fan of most American buttercreams, the simplicity of the process is a great time saver. Also, there was no trace of the “grittiness” that is sometimes present in an American buttercream.

A perfect cake and icing if you are serving a crowd. Also, quite portable in the baking pan if you need to bring a dessert to a friend’s home or to a picnic.

Zucchini season is in the summer and when it comes, people who garden often have an abundance. I’ve tried many baked zucchini items and just love zucchini baked into things. It was a no-brainer that I would try this chocolate zucchini cake with buttercream frosting recipe.

The cake is easy to make. The longest time for prep is in the shredding of the zucchini (even with a food processor but I also was weighing the zucchini as I went.) The ingredients are readily available.

By itself, the cake tastes good and this holds true for the frosting. The frosting adds time and could be skipped but is nice on the cake. (It definitely makes the cake look better.) The frosting is light with a nice flavor.

I have a secret. I baked this cake, frosted it, and only got ONE BITE of it to prepare this review.

The way I know it’s good is based on solid evidence…..

  1. There was none left after about 30 minutes on the table at a bake sale
  2. I was told multiple times what a great cake this is, and
  3. I got a lot of questions about it, and even got to brag a bit about our fantastic website and my recipe testing

I took this cake to a bake sale fundraiser where I have quite the reputation for excellent desserts (many thanks to the Leite’s website). Before I could get a piece for myself, the entire cake was gone. I had to steal a bite, and believe me, it wasn’t easy.

One thing I already knew for sure—the frosting is DREAMY. That part I had already tasted, and the recipe makes enough for a nice, thick layer.

This chocolate zucchini cake is a super easy, super moist, crowd-pleaser! And the fact that the batter comes together in one bowl is a nice bonus. It’s also a great way to use up surplus summer zucchini and sneak a few extra veggies into your diet. The chocolate buttercream frosting is just perfect and also an easy one bowl recipe.

One change I would make would be to add a little salt, espresso powder, or orange zest to the cake batter to give it a bit more depth of flavor. Other than that, this is a recipe you can make any time with ingredients you most likely have on hand.

This chocolate zucchini cake with chocolate buttercream frosting was a clear winner by all who devoured it.

And did I mention simple? Once the ingredients were gathered for the cake, the process couldn’t have been easier. No sifting, no creaming, no mixer!

Forty-five minutes later, a wonderful, super moist, slightly dense cake with a welcomed, not-too-sweet deep, chocolate flavor. The zucchini was truly the magical secret ingredient. It quietly added that unbelievable moistness, while leaving no trace whatsoever in the cake. Not one guest could guess its presence.

I was struck by the lack of any salt in this chocolate cake recipe and when I tasted only the cake, I thought a little was needed. Fear not, however, for the best is yet to come! That frosting!

The literal “icing on the cake” was the icing on this cake! I have made countless chocolate buttercream frostings, and I thought this was by far the best to date. I found the texture to be light, airy, fluffy and silky most likely owing to the beating of the frosting for the full 5 minutes.

Originally published August 2, 2022

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Comments

  1. 5 stars
    My family RAVED about this cake. I bake a cake weekly, and this recipe won top honors from my three picky children. Be sure to grate the zucchini finely to produce a silky crumb. I substituted 1/2 c of apple sauce for the oil and reduced the sugar by 1/4 c because the applesauce is sweet.

    The frosting can be scaled down to:
    2 sticks of salted butter, room temp
    scant 3 cups of powdered sugar
    1/2 c of unsweetened cocoa powder
    1 1/2 ts vanilla extract
    3 TB of heavy whipping cream.

    The original recipe for the frosting seemed too much for a sheet pan cake, in my opinion.
    Make this soon, you won’t regret it! Zucchini flavor was very mild, eclipsed by good quality cocoa. I used Barry’s Cacao extra dark.

    1. Thank you so much, Bonnie! We’re delighted to hear it was such a hit and appreciate you sharing your modifications. The cake looks absolutely wonderful.

  2. 5 stars
    I’ve made this 3x so far in the last month using random zucchini that were slightly overgrown in my garden. Each time I halved the recipe and baked in an 8×8 baking pan. I also made the buttercream recipe once (other times we had whipped cream or ice cream and even Greek yogurt) and since we’re only 2 people (plus friend tasters) I made 1/3 of the buttercream recipe and it was beyond delicious. The recipe is absolutely perfect and especially since I scaled it myself.

  3. 5 stars
    I made this today, rather warily, but it was excellent. Now definitely my favourite way to use up the courgette glut. Zucchini to you guys over the pond. I didn’t frost it, just drizzled it with melted white chocolate.

      1. 5 stars
        Really delicious – I omitted the 1/2 cup of oil and it baked up fine. I also added a 1/2 cup of mini chocolate chips! Had to leave it in the oven for an extra 3-4 min but it came out great. I also skipped the frosting – I have been avoiding butter and didn’t have any on-hand. Cake is still delicious and moist.

        1. Fantastic, Rachel! We’re so pleased you enjoyed this and a little extra chocolate is always a great idea. Please let us know what you make next.

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