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A one bowl chocolate cake in a 9x13 pan with swirls of creamy chocolate frosting and a square cut out to show the moist crumb

One Bowl Chocolate Cake

A moist, deeply chocolatey sheet cake mixed by hand in one bowl with cocoa, buttermilk and hot coffee, topped with creamy chocolate frosting.
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Prep Time 15 minutes
Cook Time 35 minutes
Cooling 1 hour
Total Time 1 hour 50 minutes
Servings: 16 pieces
Course: Dessert
Cuisine: American
Calories: 370
Ingredients Method Notes

Ingredients
  

Cake
  • 1 3/4 cups all-purpose flour spooned and leveled (220 g)
  • 1 3/4 cups granulated sugar (350 g)
  • 3/4 cup unsweetened cocoa powder sifted (65 g)
  • 1 1/2 teaspoons baking soda
  • 1 teaspoon baking powder
  • 1 teaspoon fine salt
  • 2 large eggs room temperature
  • 1 cup buttermilk room temperature (240 ml)
  • 1/2 cup vegetable oil (120 ml)
  • 2 teaspoons pure vanilla extract
  • 1 cup hot brewed coffee or hot water (240 ml)
Chocolate frosting
  • 1/2 cup unsalted butter softened (113 g)
  • 2/3 cup unsweetened cocoa powder sifted (55 g)
  • 3 cups powdered sugar sifted (360 g)
  • 1/3 cup milk plus more as needed (80 ml)
  • 1 teaspoon pure vanilla extract
  • 1 pinch fine salt

Method
 

Make the cake
  1. Heat the oven to 350°F (175°C). Grease a 9x13-inch metal pan and dust with cocoa powder or line with parchment.
  2. In a large bowl, whisk the flour, sugar, cocoa powder, baking soda, baking powder and salt until combined.
  3. Add the eggs, buttermilk, oil and vanilla and whisk for 1 minute until smooth.
  4. Slowly whisk in the hot coffee. The batter will be thin.
  5. Pour into the pan and bake for 32 to 38 minutes, until a toothpick in the center comes out clean or with a few moist crumbs.
  6. Cool completely in the pan on a wire rack, about 1 hour.
Make the frosting
  1. Beat the butter until creamy. Add the cocoa, powdered sugar, milk, vanilla and salt and beat until smooth and fluffy, adding milk a teaspoon at a time if needed.
  2. Spread the frosting over the cooled cake and cut into 16 squares.

Notes

Layer cake: Bake in two 9-inch rounds for 28 to 34 minutes and double the frosting.
Storage: Keep covered at room temperature for 2 days or refrigerated for 5 days. Freeze unfrosted for up to 3 months.
Nutrition is an estimate per piece with frosting.