Blackberry Lime Cake With Blackberry Buttercream

by Alli

Blackberry Lime Cake is a three-layer lime cake frosted with blackberry buttercream. The layers are filled with blackberry coulis and blackberry buttercream. This cake is a blackberry lover’s dream come true. It’s so pretty and delicious. 

I actually use a cake mix for this recipe. I’ve tried several homemade key lime cake recipes, but I’ve never found one I was crazy about. So, a cake mix it is, and it’s wonderful! 

Blackberry Lime Cake Is A Winner! 

Don’t let all the frou-frou words like coulis scare you. Blackberry coulis is just a fancy name for blackberry puree. The puree is used to top the middle layer of the cake and in the buttercream frosting.

Slice of 3-layer blackberry lime cake with blackberry coulis and blackberry buttercream

Unless you strain the puree, the blackberry buttercream is going to have some seeds in it. If you don’t want seeds, you can press the mixture through a sieve. I don’t mind the seeds but I can understand why some people don’t like them. 

If you’re going to strain the mixture, make sure you simmer the blackberry coulis until very thick. Of course, it will thicken some more as it cools. 

I’ve Always Loved Blackberries

When I was growing up, we always picked wild blackberries with mom’s blackberry cobbler and her famous blackberry jam in mind. For me, the blackberry seeds in the jam added to the deliciousness. I can almost taste that cold jam spread on a warm slice of buttered bread toasted to perfection in a cast-iron skillet. 

I wish I had my mom’s recipe for blackberry jam. If you have a good recipe, please share it in the comments! 

Ingredients for Blackberry Lime Cake

Here is a list of ingredients at a glance. See the recipe card at the end to get the full recipe. 

  • White cake mix
  • Vegetable oil
  • Eggs
  • Lime Jell-O gelatin
  • Orange juice
  • Fresh lime juice

Blackberry Coulis Ingredients:

  • Fresh Blackberries
  • Granulated Sugar
  • Cornstarch
  • Lime Juice
  • Water 
  • Salt

Helpful Hint: I like to make the coulis a day ahead. You can leave at room temperature for up to two days. It will last in the fridge for 4-5 days. 

Blackberry Buttercream Ingredients:

  • 1/2 of the blackberry coulis
  • Butter
  • Salt 
  • Powdered Sugar

How To Make the Blackberry Coulis

Place blackberries, lime juice, sugar, and sauce in a heavy-bottomed saucepan. Add 1/2 of the water to the blackberry mixture. Combine the remaining water with the cornstarch and mix well.

Bring the blackberry mixture to a simmer over medium heat, stirring, until sugar is dissolved. Add the cornstarch/water to the blackberries. Continue to cook on medium-low until the mixture is glossy and thickened. The color will change to a deep translucent blackberry color. 

When the mixture is thick enough to coat the back of a wooden spoon, it’s ready. You want the texture to be thick and not runny. 

Blackberry Coulis in a blue bowl

At this point, if you desire, you can strain the seeds by pushing the blackberry mixture through a sieve. Or, you can leave the seeds in like I do. Remove from the heat and let cool completely. 

How To Layer The Blackberry Lime Cake

The bottom layer is frosted with blackberry buttercream.

Bottom layer of cake topped with blackberry buttercream

The middle layer is topped with blackberry coulis.

Middle Layer of Cake topped with blackberry coulis

Finally, the top and sides of the cake are frosted with the remaining blackberry buttercream.

Blackberry Lime Cake with Blackberry Buttercream on a white platter garnished with lime slices and blackberries

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Yield: 14-16 Servings

Blackberry Lime Cake

Slice of 3-layer blackberry lime cake with blackberry coulis and blackberry buttercream

Blackberry Lime Cake is a delicious layered cake featuring Blackberry Buttercream and a Blackberry Coulis.

Prep Time 25 minutes
Cook Time 20 minutes
Total Time 45 minutes


Cake Ingredients

  • 1 package white cake mix
  • 1 (3 oz) package lime Jell-O gelatin
  • 3/4 cup orange juice
  • 1 cup vegetable oil
  • 4 eggs
  • 2 Tablespoons fresh lime juice

Blackberry Coulis

  • 2 cups fresh blackberries
  • 1/2 cup granulated sugar
  • 1 Tablespoon cornstarch
  • 2 Tablespoons fresh lime juice
  • 1/4 cup water
  • 1/4 teaspoon salt

Blackberry Buttercream

  • 1/2 of blackberry coulis
  • 8 oz. (2 sticks) unsalted butter, softened
  • 4 cups powdered sugar


  1. Preheat oven to 350º F. Grease and flour 3 8-inch cake pans.
  2. In a large mixing bowl, add the cake mix, gelatin, oil, and orange juice. Beat on low until combined.
  3. Add eggs, one at a time, beating after each addition. Add lime juice and beat for 2 minutes on medium-high, scraping sides occasionally.
  4. Bake for 20-25 minutes or until a toothpick inserted near the center of the cake comes out clean. Cool in pans for 10 minutes. Remove and place on wire racks until completely cool.
  5. To make the blackberry coulis, add the blackberries, sugar, lime juice, salt, and 1/2 of the water to a medium saucepan. (Combine the remaining water with the cornstarch and set aside.) Cook on medium-low, stirring or shaking the pan occasionally. Once the mixture begins to bubble, stir in the cornstarch/water mixture. Continue to cook on low until thick and glossy. Once the mixture coats the back of a spoon, it's done.
  6. To strain (optional) press the blackberry coulis through a sieve. Let cool completely.
  7. To make the blackberry buttercream, place the softened butter in the bowl of a stand mixer fitted with the paddle attachment. Beat until smooth, about 2 minutes, scraping down the sides as needed. Add 1/2 of the cooled blackberry coulis and beat until combined. Add the powdered sugar, one cup at a time, with the mixer on low. Once all the powdered sugar is added, increase the speed to medium-high and beat for 2 minutes.
  8. To assemble the cake, place one of the layers on a cake plate. Using an offset spatula, put a big dollop of the buttercream frosting in the middle of the cake layer (about 1 cup). Spread the frosting evenly over the top and just past the edges. Place the 2nd cake layer on top and press gently. Add the remaining blackberry coulis and spread evenly over the layer. Add the top layer, pressing gently and frost the top and sides of the cake with the remaining buttercream frosting.

Nutrition Information



Serving Size


Amount Per Serving Calories 361Total Fat 21gSaturated Fat 5gTrans Fat 1gUnsaturated Fat 15gCholesterol 62mgSodium 120mgCarbohydrates 42gFiber 1gSugar 38gProtein 3g

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