This unusual cake gets its all-natural flavor and color from an infusion of fresh blackberry purée. Whether finished with fruity whipped cream or tangy cream cheese frosting, it makes an easy summer dessert or a slightly indulgent addition to brunch.
Why It Works
- At 60°F (16°C), butter is soft but pliable and ideal for aeration, giving the cake a fine, even crumb.
- Egg whites have a neutral flavor and color, keeping the focus on fresh fruit.
- Due to their high proportion of water, egg whites emulsify best at 70°F (21°C).
- Blackberry purée replaces more typical liquid ingredients in the cake.
- Cinnamon subtly amplifies the natural flavor of the blackberries.
- The unique pH and starch behavior of bleached cake flour keeps this cake fluffy and light, despite the high moisture and acidity of fresh fruit.
- Yield:Serves 8
- Active time:25 minutes
- Total time:3 hours
- 7 ounces fresh blackberries (about 1 1/4 cups; 200g), firm and tart
- 4 ounces unsalted butter (about 8 tablespoons; 110g), softened to about 60°F (16°C)
- 5 1/4 ounces sugar (about 3/4 cup; 145g)
- 1 1/4 teaspoons baking powder
- 1/4 teaspoon baking soda
- 1/4 teaspoon (1g) Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight
- 1/8 teaspoon ground cinnamon
- 2 ounces egg whites (about 1/4 cup; 55g), brought to about 70°F (21°C)
- 5 1/2 ounces bleached cake flour (about 1 1/4 cups, spooned; 155g), such as Swans Down, sifted (see note)
- To Serve:
- 1 batch Cream Cheese Frosting
- Additional blackberries, to garnish
To Prepare: Using a blender, food processor, or immersion blender, purée blackberries until totally smooth. If seeds bother you, the purée can be strained using a fine-mesh sieve; if you do plan to strain, add a couple extra blackberries to make up for the loss. Measure out exactly 6 ounces fresh blackberry purée (about 3/4 cup; 170g) and bring to about 70°F (21°C) before using.
Adjust oven rack to lower-middle position and preheat to 350°F (180°C). Lightly grease an 8- by 2-inch or 8- by 3-inch anodized aluminum cake pan and line with parchment (explanation and tutorial here).
To Make the Cake: In the bowl of a stand mixer, combine butter, sugar, baking powder, baking soda, salt, and cinnamon. Mix on low speed to roughly incorporate, then increase to medium and beat until fluffy and light, about 5 minutes. About halfway through, pause to scrape bowl and beater with a flexible spatula.
With mixer still running, add egg whites a little at a time, letting each addition fully incorporate before proceeding to the next. Reduce speed to low and sprinkle in about 1/3 of cake flour, followed by 1/3 of prepared blackberry purée. Repeat with remaining flour and fruit, working in thirds as before.
Scrape bowl and beater with flexible spatula and resume mixing on medium speed for about 3 seconds to ensure everything is well combined. The batter should look bright purple and register between 65 and 68°F (18 and 20°C) on a digital thermometer. (Significant deviation indicates ingredients were too warm or too cold, which can lead to textural problems with the cake.) If the batter looks streaky or tie-dyed, gently fold with a flexible spatula until streaks disappear.
Scrape into prepared pan, spread into an even layer, and bake until puffed and firm, about 30 minutes. Cool directly in pan for 1 hour, then run a butter knife around the edges to loosen. Invert onto a wire rack, peel off parchment, and place on a serving plate until fully cool, about 1 hour. Top with a batch of Cream Cheese Frosting and a handful of fresh blackberries and cut with a chef's knife to serve. Wrapped in plastic, this cake will keep for up to 3 days at cool room temperature.