Blackberry Lavender Cake
Layers of fluffy vanilla cake swirled with blackberry puree, homemade blackberry cake filling, and delightfully balanced lavender buttercream. It's earthy and floral, stunning inside and out, and so perfect for summer!
Servings 15 slices
Ingredients
Blackberry Puree
- 10 Oz (283g) fresh or frozen blackberries
- 1 1/2 tsp lemon zest
- 1 1/2 tsp lemon juice
- 1 Tbsp packed light brown sugar
- 2 tsp cornstarch
- 1/4 tsp ground cinnamon
- 1/8 tsp salt
Blackberry Cake
- 2 3/4 Cups (290g) sifted cake flour*
- 2 tsp baking powder
- 1/2 tsp baking soda
- 1/2 tsp salt
- 3/4 Cup (170g) unsalted butter, room temperature
- 1 1/2 Cups (300g) granulated sugar
- 2 large eggs + 2 large egg whites, room temperature
- 1/2 Cup (120g) sour cream, room temperature
- 1 Tbsp pure vanilla extract
- 1 Cup (240ml) whole milk, room temperature
- 1/2 Cup (120ml) blackberry puree, room temperature recipe above
Lavender Buttercream
- 1/3 Cup whole milk
- 2 Tbsp dried culinary lavender
- 2 Cups (452g) unsalted butter, room temperature
- 7 Cups (840g) powdered sugar
- 2 tsp pure vanilla extract
- 1/4 tsp salt, or to taste
- 2-4 drops purple food coloring* optional
Garnish
- 6-8 fresh blackberries
Instructions
Make the Blackberry Puree
- Add the blackberries, lemon zest, lemon juice, brown sugar, cornstarch, cinnamon, and salt into a medium saucepan. Cook over high heat until the mixture begins to boil, then use a fork to mash up the berries. Continue to cook for 10-15 minutes or until the puree has thickened and reduced by about 1/3. You should have around 1 Cup of blackberry puree after the reduction. Remove from the heat and place into an airtight container in the refrigerator to let cool for about 30 minutes, or until room temperature. It will thicken as it cools.
Make the Blackberry Cake
- Preheat the oven to 350°F. Prepare three 6-inch or two 8-inch cake pans by spraying the sides with a cooking spray (Baker's Joy is my favorite) and fitting a parchment paper circle to the bottom of the pan.
- Sift the cake flour and then measure by spooning and leveling it in your measuring cup. Add the cake flour, baking powder, baking soda, and salt into a bowl and whisk to combine. Set aside.
- In the bowl of your stand mixer (a handheld mixer works fine too!), beat the butter on high for two minutes until it's light and creamy. Add in the sugar and continue to mix on medium-high for another two minutes. Turn the mixer to low and add the eggs and egg whites, one at a time, mixing until just combined and scraping down the bowl and paddle as needed. Add the vanilla and sour cream, turn the mixer to high, and beat for one full minute. It will look curdled at this point, but don’t worry – it will become smooth cake batter at the end.
- Add in the dry ingredients all at once and turn the mixer to low speed. Mix until just combined, then slowly pour in the milk. Continue to mix on low speed until just combined, about 30 seconds. Scrape down the sides and bottom of the bowl and give it a few stirs with a whisk to make sure there are no lumps. The batter will be slightly thick.
- Pour the batter evenly into the prepared cake pans. Reserve 1/2 cup of the blackberry puree for the filling (place it back into the refrigerator), then add the remaining 1/2 cup of puree by the spoonful into each batter-filled cake pan. Use a skewer or butter knife to swirl the puree into the batter, then bake for 30-35 minutes. The cake layers are done when they spring back to the touch and a toothpick inserted into the middle comes out clean or with just a few moist crumbs. Let the cakes cool in the pan for five minutes before turning them out onto a wire rack for an additional few hours of cooling. Make sure they're entirely room temperature before assembling.
Make the Lavender Buttercream
- Add the milk into a small saucepan. Cook over medium heat, stirring frequently, until the milk begins to simmer. Remove from the heat and stir in the dried culinary lavender. Let the lavender steep in the milk for 15 minutes, then strain the milk through a fine mesh sieve set over a small bowl. Press all the excess milk out of the lavender buds before discarding them. Allow the lavender milk to cool completely before adding it to the buttercream.
- In the bowl of a stand mixer fitted with the paddle attachment (a hand mixer works fine too!) cream the butter on medium-high until it’s creamy and light in color, about 5 minutes.
- With the mixer on low speed, add the powdered sugar a few cups at a time, scraping down after each addition and making sure each cup is fully incorporated before adding the next one. Add the lavender milk, vanilla, salt, and food coloring (if using) and continue mixing on low speed until fully combined and smooth, scraping down the bowl and paddle as needed.
Assembly
- Once the blackberry cakes are completely cooled, level them to your desired height. Add a swipe of lavender buttercream onto a cardboard cake circle and place the first cake layer on top. Add a few cups of lavender buttercream into a piping bag and snip off a ½ inch opening, then pipe a circle around the edge of the cake layer to create a buttercream dam. Fill in the center of the dam partially with lavender buttercream, then top with blackberry puree until you reach just below the top of the dam. Repeat the filling and stacking process with the remaining cake layers, placing the final layer on top, upside down so that the bottom of the layer is the top of the cake. Crumb coat the cake with lavender buttercream, then place it in the refrigerator for at least 30 minutes to let the buttercream set firm. If the cake layers are slipping around during the crumb coating process, wrap the whole cake tightly in plastic wrap to lock in the shape, then refrigerate until the lavender buttercream in between the cake layers is firm (about 20-30 minutes).
- To create the look pictured, reserve about 1 cup of lavender buttercream for the swirls on top, then use the rest to frost a rustic finish all over the cake. I used a small angled spatula to create the swoops and swirls. Add the remaining lavender buttercream into a piping bag fitted with Wilton Tip 1M, then pipe swirls on top of the cake spaced about ½ inch apart. Place a fresh blackberry in between each swirl.
Notes
*DIY Cake Flour Recipe: To make your own cake flour, spoon and level one cup of all-purpose flour and remove 2 Tbsp. Add 2 Tbsp of cornstarch. Repeat per the amount of cake flour you need, then sift the flour and cornstarch mixture 4 times (don’t skip that step!). After sifting, spoon and level to re-measure the amount of cake flour you need. If measuring with a kitchen scale, you’ll want to measure out 325g of homemade cake flour (since all-purpose weighs more than store bought cake flour).
*Purple Food Coloring: I used 3 drops of AmeriColor Regal Purple for the color pictured.
Make Ahead Tips:
- The blackberry puree can be made ahead and stored in an airtight container in the refrigerator for up to two days. Bring it back to room temperature before using it in the cake and buttercream recipes.
- The blackberry cake layers can be baked ahead and stored at room temperature, wrapped in plastic wrap, for up to two days. Alternatively you can store the cakes in the freezer for up to two months.
- The lavender milk (for the lavender buttercream) can be made 2-3 days ahead and stored in an airtight container in the refrigerator. Bring it back to room temperature before adding it to the buttercream.
- The lavender buttercream can be made ahead and stored in an airtight container in the refrigerator for up to two weeks. When you’re ready to use it, bring it back to room temperature and re-mix in your stand mixer to bring it back to smooth buttercream consistency.
- The assembled cake must be stored in the refrigerator (because of the fresh fruit filling). It will last 4-5 days in the refrigerator, but is freshest closer to the assembly date. When you're ready to serve, bring the cake back to room temperature by taking it out of the refrigerator 1.5-2 hours beforehand.