Blackberry Lime Cake

The best blackberry cake is made with fresh blackberries and a hint of lime. This incredibly moist and tender cake goes so well with a scoop of vanilla ice cream on a hot summer day.

Course Dessert

Cuisine American

Prep Time 30

Cook Time 30

Decorating time 1

Total Time 2

Servings cups

Calories 1550kcal

Author Elizabeth Marek

Equipment

2 8"x2" round cake pans or three 6" pans
Stand mixer with paddle and whisk attachments
Immersion blender

Ingredients

Blackberry Cake

8 ounces buttermilk slightly warm
3 ounces vegetable oil
3 large eggs room temperature
1 Tablespoon lime zest (About 1 lime)
1 Tablespoon lime juice
12 ounces all-purpose flour
11 ounces granulated sugar
1 teaspoon salt
1 teaspoon baking soda
8 ounces unsalted butter softened
2 Tablespoons all-purpose flour (For dusting on blackberries)
4 ounces blackberries (You can use frozen, but don't thaw them)

Blackberry Puree

16 ounces fresh or frozen blackberries
1 tablespoon lime zest
2 tablespoon lime juice
1 tablespoon corn starch
⅛ teaspoon salt

Blackberry Buttercream Frosting

24 ounces unsalted butter room temperature (You can use salted butter but it will affect the taste and you need to leave out additional salt)
24 ounces powdered sugar sifted if not from a bag
2 teaspoons vanilla extract
6 ounces pasteurized egg whites room temperature
2 ounces blackberry puree (You can add more if you want to)
1 drop Americolor electric pink food coloring (Optional)

US Customary - Metric

Instructions

Blackberry Puree

Combine lime juice and cornstarch to make a slurry and mix until there are no lumps.
Mix the blackberries and salt in a saucepan and use an immersion blender to make the filling smooth.
Turn on the heat and cook down the berries. Keep stirring to keep the puree from cooking too quickly on the bottom of the pan.
Once the puree has thickened up slightly, remove it from the heat and stir in the lime zest.
Transfer the puree to a large bowl to cool to room temperature. You will use about 6 Tablespoons of the puree to add to your cake. About ¼ to ½ cup of puree will be for the buttercream. If you choose to strain the seeds out of all of the puree, add a couple of extra ounces of berries to account for the loss in straining. I chose to leave the seeds in for the cake and strain the seeds out for the buttercream. The seeds can be left in for the buttercream too, your choice.
Store leftover puree in the fridge for up to a week or freeze for 6 months.

Making Blackberry Cake

Heat oven to 335º F/168º C and prepare two 8"x2" round cake pans with cake goop or another pan release and parchment paper if you prefer.
Measure out the buttermilk and place 4 oz in a separate measuring cup. Add the oil to the 4oz of buttermilk and set aside.
Add your eggs and lime zest to the remaining milk and gently whisk to combine. Keep the lime juice separate, you will add this at the end.
Place the flour, sugar, baking soda, and salt into the bowl of your stand mixer with the paddle attachment. I'm using my Bosch universal plus mixer but you can use a hand mixer, just mix for longer.
Turn the mixer onto the slowest speed (setting 1 on Kitchen Aid mixers). Slowly add chunks of your softened butter until it is all added. Let everything mix until it looks like coarse sand.
Add your milk/oil mixture all at once to the flour mixture. Mix on medium (speed 4 on KitchenAid) for 1 full minute to develop the structure. Don't worry, this will not over-mix the cake. Because it is AP flour you do not need to mix as long as cake flour (more gluten, less time needed).
Scrape the bowl. This is an important step. If you skip it, you will have hard lumps of flour and unmixed ingredients in your batter. If you do it later, they will not mix in fully.
Slowly add in the rest of your milk/eggs/zest ingredients in 3 parts. Next, pour in the lime juice with the last addition of liquid, stopping to scrape the bowl one more time halfway through. Your batter should be thick and not too runny.
Fill your pans ½ full with cake batter.
Spoon about 2 tablespoons of room-temperature puree over the batter. Use a small spatula or knife to gently fold the puree in to create a swirl effect into the batter.
Add the floured blackberries to the top of the batter. Do not push them down as their weight will cause them to sink anyway as the cake heats up.
Place the cakes in the preheated oven. I start by baking for 30 minutes for 6" and 8" cakes and 35 minutes for 9" and larger cakes and then checking for doneness. If the cakes are still really jiggly, I add another 5 minutes. I check every 2 minutes after that until I'm close and then it's every 1 minute. Cakes are done when a toothpick inserted in the center comes out with a few crumbs.
After the cakes have cooled for 10 minutes or the pans are cool enough to touch, place a wire rack on top and flip the cakes over to remove them from the pans. Let them rest on a cooling rack to cool completely, or wrap in plastic wrap and chill in the freezer.

Making Blackberry Buttercream

Strain out the seeds of the blackberry filling. This is optional but it will make a smoother texture when scraping the sides.
Place the egg whites and powdered sugar in the bowl of your stand mixer with the whisk attachment and whip on high speed for 3-5 minutes. An electric mixer and a large mixing bowl will also work, just mix for longer.
Add the softened butter in small chunks then vanilla and salt. Whip on high until light and fluffy and white, about 8 to 10 minutes.
Add about ½ cup of the blackberry purée to the buttercream and continue to whip until combined.
Mix in about 1-2 drops of pink food coloring to enhance the color if you choose.
Optional: switch to the paddle attachment and mix on low for 15-20 minutes until all air bubbles are gone.
Stored it in an airtight container for up to a week in the refrigerator or for 3 months in the freezer.

Decorating the blackberry cake

Once your cakes are chilled, trim off the dome and brown edges of the cake. This is optional but makes for pretty slices.
Place your first cake layer onto a board.
Spread on about ¼" of your blackberry buttercream.
Layer some fresh blackberries into the buttercream.
Spread some more buttercream on top of the blackberries and then add your next layer of cake.
Repeat the process with layer two and then add your final layer of cake on top.
Cover the whole cake in a thin layer of buttercream. This is the crumb coat.
Place the cake into the fridge or freezer for 20 minutes to set the buttercream layer.
Apply your final coat of buttercream and use a bench scraper and offset spatula to make it nice and smooth.
Decorate the top of the cake with more dollops of buttercream, fresh berries and some lime zest. I used a 1M piping tip for this design.

Video

Notes

To keep the blackberries and puree from turning blue and green during baking the acidity level had to be higher, when the acidic berries touch the alkaline they oxidize and turn green. Lowering the alkalinity of the batter kept the blackberries that nice deep purple red color.
I used AP flour in this recipe because the cake needed just a little more structure to hold those big juicy berries. AP flour has more protein, less starch, so is just a little stronger than cake flour. The higher acid in the batter tenderizes the gluten proteins as well, so you do not end up with a tough cake. Too much acid in the batter will cause the protein to become too weak and the cake will be crumbly and dense. It's a very fine balance to find the right texture and keep the colors bright!

Nutrition