Blackberry Cake with Blackberry Buttercream

Directions

1. Make the Blackberry Purée:
   In a saucepan, combine blackberries, salt, lime juice, and cornstarch slurry. Blend with an immersion blender until smooth, then cook over medium heat, stirring constantly, until the mixture thickens slightly. Remove from heat, stir in lime zest, and let cool to room temperature. Reserve about 6 tablespoons for the cake and the rest for your buttercream.
2. Prepare the Cake Pans:
   Heat your oven to 335°F (168°C). Grease two 8-inch cake pans with pan release or parchment.
3. Mix the Liquid Ingredients:
   Measure out your buttermilk. Place 4 oz in a small cup and whisk in the vegetable oil. In another bowl, combine the remaining buttermilk, eggs, and lime zest. Keep lime juice separate.
4. Combine the Dry Ingredients:
   In a stand mixer fitted with a paddle, add flour, sugar, salt, and baking soda. Mix on low speed.
5. Add Butter to the Dry Ingredients:
   Add softened butter, a few chunks at a time, mixing until the mixture looks like coarse sand.
6. Add the Milk–Oil Mixture:
   Pour the 4-oz buttermilk and oil mixture into the bowl and mix on medium for 1 full minute. Scrape the bowl well.
7. Add Remaining Liquids:
   Add the remaining milk–egg mixture in three additions. Add the lime juice with the last portion. Scrape the bowl again so the batter mixes evenly.
8. Add the Blackberry Swirl:
   Pour batter into pans until they’re halfway full. Spoon about 2 tablespoons of blackberry purée over each pan of batter and gently swirl with a knife.
9. Add the Blackberries:
   Dust the blackberries with 2 tablespoons flour and scatter them on top of the batter (they will sink naturally while baking).
10. Bake the Cakes:
    Bake 8-inch cakes for 30–38 minutes, checking often during the last few minutes. The cake is done when a toothpick comes out with a few moist crumbs. Cool cakes in their pans for 10 minutes, then turn out onto racks to cool completely. Chill in the freezer before decorating.
11. Make the Buttercream:
    Beat the butter until creamy. Add powdered sugar, vanilla, and egg whites and mix until smooth and fluffy. Add blackberry purée (strained or not — your choice). Add optional pink food coloring for a stronger berry-pink tone.
12. Assemble the Cake:
    When the cakes are chilled and firm, trim edges if desired. Spread blackberry buttercream between layers and add fresh berries. Apply a crumb coat, chill, then finish with a final smooth layer of buttercream. Decorate with berries and lime zest.

Recipe Details

• Prep Time: 45 minutes
• Cook Time: 30–40 minutes
• Total Time: 1 hour 30 minutes
• Servings: 12 slices
• Difficulty Level: Medium / Advanced

Variations & Substitutions

• Swap blackberries for raspberries or blueberries for a different fruity twist.
• Add 1 teaspoon of lavender to the purée for a floral variation.
• Use lemon instead of lime for a brighter citrus profile.
• Substitute part of the buttercream with cream cheese frosting for more tang.

Serving Suggestions