Introduction

This one-bowl chocolate cake is a simple yet indulgent treat perfect for any occasion. Moist and rich, it combines a tender crumb with a luscious homemade cocoa frosting, all made with minimal fuss and everyday ingredients.

A close-up of a single piece of chocolate cake on a white plate, showing two layers: a thick, dark brown spongy cake base with a moist and crumbly texture, topped by a shiny, smooth layer of dark chocolate glaze that slightly drips down the sides. The background is a white marbled texture, creating a clean and simple setting. photo taken with an iphone --ar 4:5 --v 7

Ingredients

1 cup all-purpose flour
1 cup granulated sugar
¼ cup unsweetened cocoa powder (for the cake)
1 teaspoon baking soda
½ teaspoon baking powder
¼ teaspoon salt
1 large egg
½ cup vegetable oil
½ cup buttermilk
½ cup hot water
5 tablespoons unsalted butter (for the frosting)
¼ cup unsweetened cocoa powder (for the frosting)
1 ¼ cups powdered sugar
2 to 3 tablespoons milk
½ teaspoon vanilla extract

Instructions

Step 1: Line an 8-inch square or round cake pan with parchment paper or aluminum foil and set aside.
Step 2: Preheat your oven to 350°F (175°C).
Step 3: In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Step 4: Add the egg, vegetable oil, and buttermilk to the dry ingredients, then whisk until combined. Pour in the hot water and whisk again until the batter is smooth.
Step 5: Pour the batter into the prepared cake pan and gently tap it on the counter to release any air bubbles.
Step 6: Bake for 25 to 30 minutes, or until a toothpick inserted into a few spots comes out clean.
Step 7: Allow the cake to cool while you prepare the frosting.
Step 8: To make the frosting, melt the butter in a saucepan over medium-low heat.
Step 9: Add the cocoa powder to the melted butter and whisk together. Cook for about 2 minutes without boiling, then remove from heat.
Step 10: Sift in the powdered sugar and whisk until smooth. Stir in vanilla extract and add milk one tablespoon at a time until the frosting is shiny and spreadable.
Step 11: Pour the warm frosting over the cake and spread evenly with a spatula. Let the cake cool completely before slicing and serving.

Tips & Variations

Use brewed coffee instead of hot water to deepen the chocolate flavor.
For a dairy-free version, substitute buttermilk with almond milk mixed with a teaspoon of lemon juice.
Try adding a pinch of cinnamon or instant espresso powder to the batter for a flavor twist.
Make cupcakes instead by dividing the batter into a muffin tin and reducing baking time to 18–20 minutes.

Storage

Store the cake in an airtight container at room temperature for up to 2 days or in the refrigerator for up to 5 days. If refrigerated, allow the cake to come to room temperature before serving for the best texture. Leftover cake can be frozen for up to 2 months; thaw overnight in the fridge.

How to Serve

A single square piece of chocolate cake sits on a white plate, showing two clear layers: a thick, moist dark brown cake base with a light, crumbly texture and a smooth, glossy dark chocolate frosting layer on top that is thick and shiny with slight ridges made by spreading. In the background, there are more pieces of the same chocolate cake blurred out on white plates, all placed on a white marbled surface. The scene has soft natural lighting highlighting the moistness of the cake and the shine of the frosting. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use regular milk instead of buttermilk?

Yes, you can make a buttermilk substitute by adding 1 tablespoon of lemon juice or vinegar to ½ cup of milk. Let it sit for 5 minutes before using.

Why does the recipe call for hot water?

The hot water helps to bloom the cocoa powder, enhancing the chocolate flavor and ensuring a smooth, moist cake texture.