1½cups3 sticks or 12 oz unsalted butter, softened, room temperature
2¼cups15.75 oz sugar
6ozegg whitesroom temperature (approximately 6 egg whites)
¾ozsour cream, room temperature
2 ¾cups all-purpose floursifted
1tablespoons all-purpose floursifted
3½ tablespoons cornstarchsifted
2cupsunsalted butterroom temperature
12ozcream cheese full fatroom temperature
Preheat the oven to 350 degrees F. Butter and lightly flour three 9-inch cake pans. Set aside.
Puree 21 oz of fresh blackberries until smooth. Using a fine-mesh strainer, strain the puree. Set aside.
In a large bowl, sift flour, baking powder, baking soda, cornstarch, cinnamon, and salt together.
In a stand mixer bowl, mix cream butter and sugar to get a smooth consistency. While mixing, add each egg white one at a time, followed by sour cream and vanilla.
Add flour in thirds, alternating with blackberry purée. Use a spatula to scrape down the sides and the bottom of the bowl when necessary.
Evenly distribute batter among prepared cake pans (approximately 3 cups each) and level the batter.
Bake for 30-35 minutes, until an inserted toothpick or knife comes out clean. Let the blackberry cake layers cool down to room temperature, or wrap with plastic and refrigerate.
Cream Cheese Frosting:
Use an electric hand mixer (or stand mixer with paddle) to beat together cream cheese and butter until incorporated and then add powdered sugar, salt, and vanilla. Mix on low speed until smooth.
Place one layer on a cake stand or serving plate. Top it with approximately 3/4 cup of frosting and spread evenly. Add 5 oz of fresh blackberries across the layer. Repeat with the second layer of cake. Add the final layer, frost it, and smoothen the outside using just a thin coat around the cake’s sides. Decorate the top of the now-ready blackberry cake with the remaining fresh berries.
You’ll need approximately 21 oz of fresh blackberries to make the purée.
You can use a blender/immersion blender to achieve a smooth puree.
The final strain should come to approximately 12 ounces.
If you’d like to achieve a redder color batter, add puréed blackberries to a small sauce over medium heat for 5-7 minutes. Then bring to room temperature before you proceed.
You can also use three 8-inch cake pans. Fill 1 to 2-inch cake pans ½ full with batter and 3 to 4-inch pans ⅔ full with batter.