This chocolate cake recipe keeps the occasion flexible: one rectangular cake, a soft cocoa crumb, and a layer of chocolate buttercream that you can spread with the back of a spoon. There are no layers to balance and no filling to contain. Cut it into squares for a birthday table, a shared dessert or a small celebration that does not need a decorating project.
I like a cake that looks inviting before anyone reaches for a piping bag. A few broad swirls of frosting and a clean slice through the chocolate crumb are plenty for me.
Start with cocoa you can identify
Use natural unsweetened cocoa powder for this version. It supplies the chocolate flavor without adding sugar, and it sits alongside buttermilk, baking soda and baking powder in the batter. A container of sweetened drinking chocolate is a different ingredient and will change the balance.
Dutch-process cocoa has been treated to reduce its acidity, and black cocoa is more heavily alkalized. Neither is the default choice for this recipe. If the labels on your shelf are confusing, the cacao versus cocoa guide is a useful place to start. Follow the specified powder rather than changing the leavening by guesswork.
Neutral oil gives the cake a soft texture, while butter belongs in the frosting for flavor and structure. Use cultured low-fat buttermilk and large eggs. The small amount of vanilla extract rounds out the cocoa; it does not need to be the most expensive bottle in the shop.
A pourable batter is exactly what you want
Measure the flour by weight if you can. If using cups, spoon flour into the cup and level the top instead of pressing the cup into the bag. Extra flour can make a cake feel dry even when the oven timing is right. Break up visible cocoa lumps before the liquid goes in.
Whisk the dry ingredients in one bowl and the buttermilk, eggs, oil and vanilla in another. Combine them, then slowly stir in the hot water. The batter becomes noticeably thinner at this point. Do not add flour to make it look like a thicker butter-cake batter; the water is part of the formula.
Scrape the bottom of the bowl with a flexible spatula so no pockets of flour remain, then stop mixing. Pour into the prepared pan and get it into the preheated oven. You do not need to beat this batter until it is airy, and there is no butter-and-sugar creaming stage to work through.
Bake the center, then give it time to cool
Use a 9-by-13-inch metal cake pan at least 2 inches deep. A parchment sling helps with removal, but serving the cake straight from the pan is the easier option. Keep the oven rack near the middle so the top and bottom have room around them.
Start checking near 30 minutes rather than treating the timer as a promise. The center should be set, with no liquid wobble, and a toothpick should come out without wet batter. A few moist crumbs are fine. If the middle is still wet, give it a few more minutes and check again.
Set the pan on a rack and let the cake cool completely before frosting. Plan on about two hours, though a warm kitchen or a heavy pan can take longer. A warm cake softens buttercream from underneath, so a top that feels barely cool while the pan is still warm is not ready.
Soft frosting, simple slices and sensible storage
Beat softened butter until smooth, then add sifted powdered sugar and cocoa in stages at low speed. Add vanilla, a small pinch of salt and enough milk to make it spreadable. You want a frosting that holds a soft ridge, not one that runs from the spatula. If it is too firm, add milk a teaspoon at a time.
Spread the buttercream over the cooled cake, working from the center toward the edges. Fifteen pieces means three rows by five columns. Wipe the knife between cuts for cleaner squares, or leave the cake whole and let people choose their portion. The frosting quantity covers the top; it is not intended for elaborate borders or filling extra layers.
- Make ahead: bake and cool the cake, cover it well, and frost the next day.
- After frosting: keep covered in the refrigerator and use within four days. Let individual slices soften briefly before serving.
- Freeze for later: wrap cooled unfrosted portions well and freeze for up to two months for best quality. Thaw wrapped in the refrigerator, then frost.
Chocolate Cake Recipe
Ingredients
- 2 cups all-purpose flour 240 g, spooned and leveled
- 325 g granulated sugar about 1 5/8 cups
- 65 g natural unsweetened cocoa powder about 3/4 cup; not sweetened drinking chocolate
- 1 1/4 teaspoons baking powder 5 g
- 1 teaspoon baking soda 5 g
- 2/3 teaspoon fine salt 4 g
- 1 cup cultured low-fat buttermilk 240 ml
- 2 large eggs about 100 g without shells
- 1/2 cup canola oil 120 ml, about 110 g
- 2 teaspoons vanilla extract about 8 g
- 3/4 cup hot water 180 ml
- 3/4 cup unsalted butter 170 g, softened
- 260 g powdered sugar about 2 1/4 cups, sifted
- 45 g natural unsweetened cocoa powder about 1/2 cup, sifted
- 1/4 cup whole milk 60 ml; add gradually as needed
- 1 teaspoon vanilla extract about 5 g
- 1 g fine salt a scant 1/4 teaspoon
Equipment
- 1 9-by-13-inch metal cake pan at least 2 inches deep
- 2 Mixing bowls
- 1 Whisk
- 1 electric hand mixer
- 1 Wire cooling rack
- 1 flexible spatula
Instructions
- Heat the oven to 350°F (175°C), with a rack near the center. Line a 9-by-13-inch metal pan, at least 2 inches deep, with parchment across the base and sides. Leave a little overhang if you plan to lift the cake out.
- Whisk flour, sugar, cocoa, baking powder, baking soda and salt in a large bowl, breaking up cocoa lumps. In another bowl whisk buttermilk, eggs, oil and vanilla. Add the wet mixture to the dry and whisk just until combined. Slowly stir in the hot water. Scrape the bowl’s bottom and sides; the finished batter should be pourable.
- Pour the batter into the prepared pan. Bake for about 30–38 minutes, until the center is set and a toothpick comes out without wet batter; a few moist crumbs are fine. Begin checking at 30 minutes and avoid overbaking.
- Place the pan on a rack and let the cake cool completely, about 2 hours or longer if needed. Do not frost while the cake or pan still feels warm.
- Beat the softened butter with an electric mixer until smooth. Add sifted powdered sugar and cocoa in several additions on low speed. Add vanilla, salt and about half the milk. Beat until creamy, then add more milk a teaspoon at a time as needed for a soft, spreadable frosting; you may not need all of it.
- Spread frosting over the cooled cake, making broad swirls with a spoon or spatula. Cut into 15 squares, three rows by five columns. Keep the frosted cake covered in the refrigerator and use within 4 days; let individual slices soften briefly before serving.
Nutrition
Video
Notes
Tried this recipe?
Let us know how it turned out!Sources
- King Arthur Baking: natural and Dutch-process cocoa
- King Arthur Baking: chocolate cake pan and doneness guidance
- Preppy Kitchen: sheet cake preparation and frosting
- USDA FoodData Central: ingredient composition data
Hi, I’m Laura, the voice behind Tastiva. I’ve always believed that eating well should feel enjoyable, comforting, and realistic—not like another complicated rule to follow. I love creating recipes that fit into everyday life, sharing simple nutrition ideas, and finding small ways to make meals feel a little better without losing the pleasure of good food.