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Blackberry Cake with Coconut Cream Cheese Frosting

Serves 12-16     adjust servings

This vibrant Blackberry Cake uses a yellow cake mix and a box of raspberry jello to make an incredibly moist and flavorful cake! We fold in frozen blackberries before baking, meaning this cake is full of bright summer flavor. And it is so easy you can't mess it up!


For the cake

  • 1 (15.25 ounce) box yellow cake mix
  • 1 (6 ounce) box of raspberry Jell-O gelatin
  • 4 eggs
  • 3/4 cup vegetable oil (I like to use light olive oil)
  • 1 (16 ounce) bag frozen blackberries, still frozen* (fresh berries work too)

For the frosting

  • 1/2 cup (1 stick) butter, softened
  • 1 (8 ounce) package cream cheese, softened
  • 4 cups powdered sugar
  • 2 tablespoons milk, or more to taste
  • 1/2 teaspoon kosher salt
  • 1/4 or 1/2 teaspoon coconut extract, optional


  1. Preheat the oven to 350 degrees F. Use nonstick spray or butter to grease a 9x13 inch cake pan. Set aside.
  2. In large bowl or stand mixer, combine dry cake mix, dry Jello powder, 4 eggs, and 3/4 cup light tasting olive oil on high speed with electric mixer for about 2 minutes on medium speed. Remember to scrape the sides and bottom of the bowl and mix again. 
  3. Fold in the frozen blackberries. The batter is already pretty thick, and when you add the frozen berries, it solidifies even more, so just be aware that it is very thick and a bit difficult to stir. 
  4. Pour the batter into the prepared 9x13-inch pan. Use a very sturdy spatula to scrape it all in. You might think you are working with an enormous wad of chewed bubblegum at this point, but don't worry, it turns into a delicious cake, I promise.
  5. Bake at 350 for about 40-45 minutes. The cake will turn rather brown on top. Browner than a normal cake. Cover it with foil in the last 10-20 minutes if you're worried about it. You will know the cake is done when the center is not wobbly, the cake is pulling away from the edges of the pan, and when a toothpick inserted in center comes out clean, meaning there is no pink wet batter on it.
  6. Allow cake to cool completely on a wire rack. When I am feeling impatient (always) I stick it in the freezer for a while (after it's been out of the oven for at least 20 or 30 minutes)
  7. Make the frosting: In a large bowl or stand mixer, beat the butter until it is smooth, scraping the sides and bottom of the bowl. 
  8. Add the softened cream cheese and beat together until smooth, scraping sides. 
  9. Add 4 cups of powdered sugar and 2 tablespoons milk. Beat until the mixture has formed a smooth frosting, scraping the sides every now and then. 
  10. Add 1/2 teaspoon kosher salt (add less if you have table salt). Add in the coconut extract if you are using it. You should use it! Beat it all together. Add a little more milk a teaspoon at a time if you want a thinner frosting. 
  11. Use an offset spatula to spread the frosting over the cooled cake. 
  12. I like to serve this right away at room temperature, but it's also very good if you cover and let it chill in the fridge for a couple hours. Perfect for summer! You can store the frosted cake on the counter for several days, or in the fridge for up to a week.