Lemon Zucchini Cake

This moist lemon zucchini cake baked in a square pan is a user-friendly dessert that’s perfect for small gatherings. Made with yellow summer squash (or zucchini) and a touch of lemon emulsion, it offers a delicate citrus flavor, while the vibrant lemon buttercream frosting delivers a bold, tangy punch. The all-butter batter creates a rich, tender crumb, with an optional avocado oil variation for a lighter texture. No complicated decorating needed—just spread on the frosting and enjoy a manageable-sized cake that serves 9!

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Prep Time:15

Cook Time:35

Cooling Time:40

Total Time:1 30

Servings: slices

Author: Julie Gavin

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Ingredients

For the Lemon Zucchini Cake

1 ½ c. (180 g) zucchini grated (or yellow squash)
1 ¾ c. (210 g) unbleached all-purpose flour (RECOMMEND WEIGHING)
1 tsp baking powder
½ tsp baking soda
½ tsp salt
1 c. (200 g) granulated sugar
¾ c. (170 g) salted butter melted and cooled (see note for a lighter cake)
2 large eggs
2 tbsp. lemon zest from 2 medium lemons
¼ c. (60 g) lemon juice fresh is best
1 tsp. vanilla extract
1 tsp. lemon emulsion

For the Lemon Buttercream Frosting

½ c. (113 g) salted butter room temperature
2 c. (240 g) powdered sugar sifted
1 ½ tsp. lemon juice fresh is best
2 tsp. lemon zest from 1 small lemon
¼ tsp. vanilla extract
⅛ tsp. salt
1 ½ tsp. heavy cream or milk, plus more if needed for consistency

Instructions

Preheat and Prep: Preheat oven to 350°F (175°C). Grease a 9x9-inch square baking pan.
Grate the Zucchini or Squash: Grate 1 medium zucchini or yellow summer squash to yield 1 ½ cups (180 g) lightly packed. Don’t squeeze out moisture—it keeps the cake tender. Set aside.
Mix Dry Ingredients: In a medium bowl, whisk flour, baking powder, baking soda, and salt until combined. Set aside.
Combine Wet Ingredients: In a large bowl, whisk granulated sugar and melted butter until smooth. For a lighter cake, use ¼ cup (56 g) avocado oil and ½ cup (113 g) butter). Add eggs, lemon zest, lemon juice, vanilla extract, and lemon emulsion, whisking until smooth.
Make the Batter: Add dry ingredients to wet ingredients in two additions, stirring gently with a spatula until just combined. Avoid overmixing.
Add Zucchini or Squash: Fold in grated zucchini or yellow summer squash until evenly distributed.
Bake: Pour batter into the prepared 9x9 pan and smooth the top. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs. If using avocado oil, check at 30 minutes. Cool in pan completely.
Prepare Lemon Buttercream: Beat softened butter with an electric mixer on medium speed until creamy, about 1 minute. Gradually add sifted powdered sugar, lemon juice, lemon zest, vanilla extract, and salt. Beat for 1–2 minutes until fluffy. Add heavy cream or milk, 1 teaspoon at a time, if needed for spreadable consistency.
Frost and Serve: Spread lemon buttercream evenly over the cooled cake, creating and even layer. Garnish with extra lemon zest or lemon slices, if desired. Cut into 9 or 12 squares and serve at room temperature.

Notes

Zucchini or Squash: Zucchini and yellow summer squash both work beautifully in this lemon zucchini cake, adding moisture and tenderness. Don’t squeeze out liquid; if very watery, lightly pat with a paper towel.
Avocado Oil Option: For a lighter texture, use ¼ cup (56 g) avocado oil in place of ¼ cup butter. It adds moisture and a neutral flavor, complementing the butter’s richness.
Lemon Emulsion: The 1 tsp lemon emulsion enhances the cake’s subtle citrus flavor. For a stronger note, try 1 ½ tsp, but taste-test to avoid overpowering.
Why a 9x9 Pan?: The 9x9 pan is user-friendly, requiring no complicated decorating—just spread on the frosting! It yields a manageable size (9–12 servings), perfect for small gatherings without excess leftovers. If using an 8x8-inch pan, increase baking time by 3–5 minutes.
Storage: Store frosted cake in an airtight container at room temperature for up to 2 days or in the fridge for up to 5 days. Bring to room temperature before serving. Unfrosted cake can be frozen for 3 months; thaw before frosting.