Ingredients:

  • 2 cups (250g) all-purpose flour
  • 1 cup (200g) granulated sugar
  • 1/2 cup (45g) unsweetened cocoa powder
  • 1 tsp (5g) baking soda
  • 1/2 tsp (3g) baking powder
  • 1/2 tsp (3g) salt
  • 1 cup (230ml) buttermilk, room temperature
  • 1/2 cup (115g) unsalted butter, melted
  • 2 large eggs, room temperature
  • 1 tsp (5ml) vanilla extract
  • 2 cups (230g) grated zucchini, squeezed slightly to remove excess water
  • 1/2 cup (115g) unsalted butter
  • 1/4 cup (60ml) buttermilk
  • 3 tbsp (25g) unsweetened cocoa powder
  • 2 cups (400g) powdered sugar
  • 1 tsp (5ml) vanilla extract

Instructions:

  1. Preheat oven to 350°F (175°C). Grease an 18x13 inch rimmed baking sheet or line it with parchment paper. In a large bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt until no lumps remain.
  2. In a separate bowl, whisk melted butter, buttermilk, eggs, and vanilla until smooth. Stir the wet mixture into the dry ingredients using a spatula and gently fold in the grated zucchini until just combined.
  3. Spread the batter evenly across the prepared sheet pan. Bake for 20–25 minutes, or until the edges slightly pull away from the pan and a toothpick inserted into the center comes out clean.
  4. While the cake is still hot, prepare the frosting by simmering butter, buttermilk, and cocoa in a saucepan for 1 minute. Remove from heat, whisk in powdered sugar and vanilla until glossy, then pour over the warm cake and spread to the edges.