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+ servings
slice of blueberry cake on plate
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5 from 5 votes

Blueberry Birthday Cake

This blueberry birthday cake is super soft, fluffy, and moist. It’s filled with blueberry filling and the best blueberry cream cheese frosting ever. The cake tastes like blueberry with a touch of lemon (don’t add lemon zest if you don’t like the taste of lemon). The filling reminds me of blueberry pie! It’s the perfect blueberry cake for any birthday. It has so much blueberry flavour.
Prep Time40 mins
Cook Time20 mins
Total Time1 hr
Course: Baking, Cake, Dessert
Cuisine: American
Keyword: birthday cake, blueberry birthday cake, blueberry cake, blueberry cake filling, blueberry oreo cake, blueberry pie filling
Servings: 10 people
Author: Mary

Ingredients

Cake Layers

  • ¾ cup unsalted butter softened
  • ¼ cup vegetable oil any light tasting oil works
  • 1 ¼ cup granulated sugar
  • teaspoon sea salt
  • 4 large eggs room temperature
  • ½ cup sour cream room temperature
  • 1 tablespoon pure vanilla extract
  • 3 tablespoons lemon juice about 1 lemon
  • 1 tablespoon grated lemon zest about 1 lemon
  • 3 ⅓ cup all purpose flour (400g)
  • 1 tablespoon baking powder
  • ½ teaspoon baking soda
  • ¾ cup buttermilk room temperature
  • 1 ½ cups blueberries fresh or frozen - do not thaw
  • 1 tablespoon all purpose flour

Blueberry Filling

  • 2 cups blueberries fresh or frozen
  • ½ cup granulated sugar
  • 3 tablespoons lemon juice about 1 lemon
  • 1 tablespoon cornstarch
  • ½ teaspoon cinnamon ground

Blueberry Cream Cheese Frosting

  • 4-6 tablespoons blueberry filling
  • 1 cup unsalted butter softened
  • 4 cups powdered sugar sifted
  • 4 oz cream cheese softened for 10 minutes

Assembly

  • 5 oreo cookies crushed
  • ¼ cup fresh blueberries optional
Makes: 8inch round

Instructions

Cake Layers

  • Preheat oven to 355°F (180°C). Grease three 8” round baking pans with a cold bit of butter or cooking spray. Line the bottoms with a round of parchment paper.
  • In a large bowl or stand mixer, combine butter, oil, sugar, and salt. Beat until light and fluffy, scraping down the bowl halfway. This will take a minute or two.
    ¾ cup unsalted butter, ¼ cup vegetable oil, 1 ¼ cup granulated sugar, ⅛ teaspoon sea salt
  • Add room temperature eggs one at a time, beating well to combine in between and scraping down the bowl.
    4 large eggs
  • Add vanilla, sour cream, lemon juice, and zest. Beat well to combine.
    ½ cup sour cream, 1 tablespoon pure vanilla extract, 3 tablespoons lemon juice, 1 tablespoon grated lemon zest
  • Sift half of the flour, all of the baking powder, and all the baking soda into the same bowl. Fold until mostly incorporated. Sift in the rest of the flour and add the buttermilk. Fold just until no more dry streaks of flour remain.
    3 ⅓ cup all purpose flour, 1 tablespoon baking powder, ½ teaspoon baking soda
  • In a separate bowl, combine blueberries and flour. Mix to coat and add the blueberries into the batter. Don’t add any dry bits of flour at the bottom of the blueberry bowl into the batter.
    1 ½ cups blueberries, 1 tablespoon all purpose flour, ¾ cup buttermilk
  • Divide evenly into lined baking tins. Use an ice cream scoop or scale to divide evenly. Smooth out the tops and bake. If they don’t all fit in the oven you can place one of the cake layers in the fridge until the others finish baking.
  • Bake for 20-25 minutes. Check if they’re ready with a toothpick - it should come out mostly clean with a few crumbs attached. Let cake layers cool for 5 minutes in their pans before running a knife along the outside of the cake to help release and flipping upside down on a cooling rack. Let cool completely.

Blueberry Filling

  • In a saucepan, combine blueberries, sugar, lemon juice, cornstarch, and cinnamon. Heat on medium-low heat until the blueberries release their juice. Make sure to stir frequently so it doesn’t burn. You can add a tablespoon or two of water if needed to help prevent from burning.
    2 cups blueberries, ½ cup granulated sugar, 3 tablespoons lemon juice, 1 tablespoon cornstarch, ½ teaspoon cinnamon
  • Stir frequently until the mixture simmers and thickens. If your mixture isn't as thick as pie filling: mix together 1 teaspoon extra cornstarch+1 teaspoon sugar and add to the simmering filling to thicken more.
  • Transfer to a heat safe non-metal container to cool completely and chill in the fridge until ready to fill the cake.

Blueberry Cream Cheese Frosting

  • Set aside about half of the blueberry filling mixture. Puree the remaining half (about 4-6 tablespoons) with a blender or immersion blender. Alternatively, mash well with a fork until all the blueberries are broken up.
    4-6 tablespoons blueberry filling
  • Start off with softened butter, making sure that it isn’t too soft. You should be able to make an indent on the butter with your finger without getting a greasy residue all over it.
    1 cup unsalted butter
  • In a large bowl or standmixer, beat the butter until light and fluffy. Add sifted powdered sugar, half a cup at a time. Beat until light and fluffy. Scrape down the bowl frequently.
    4 cups powdered sugar
  • Beat until it becomes very light in colour and fluffy. This will take about 5 minutes.
  • Add cream cheese, piece by piece, beating well in between. Beat until light and fluffy.
    4 oz cream cheese
  • Add the blueberry puree tablespoon by tablespoon. Beat well between each tablespoon. Add about 4-6 tablespoons until it becomes fluffy and purple. Don’t add too much or it may split the frosting and make it too thin (gloopy). Add blueberry puree gradually and keep an eye on it.
  • Using a spatula, fold the frosting to remove any large air pockets and bubbles before frosting. This makes a smoother frosting.

Assembly

  • Fill a piping bag fitted with a star tip (or just the end cut off) with the frosting. You can also use a resealable plastic food bag with the end cut off.
  • On a cake board or serving plate, place a small dollop of frosting. Place the first cake layer down. Spread a thin layer of frosting on top and pipe a border of frosting that’s at least 1.5” thick and 0.5” tall.
  • Fill the middle with 2-3 tablespoons of blueberry filling, spreading it out to the frosting border. Don’t add too much filling or the cake will slide around. Add the next cake layer and repeat the process.
  • Add the third, top layer of cake. Pop the cake into the freezer for 10 minutes so the frosting sets and the cake is more stable. Keep the unused frosting in the fridge (if you keep the frosting in the fridge for longer than 15 minutes you’ll have to beat until light and fluffy again).
  • Cover the top and sides with frosting. Make sure you leave some frosting to pipe on top. Smooth the sides down with a metal spatula or cake scraper.
  • Pipe the remaining frosting into a border on top of the cake. Fill the middle of the cake with the remaining blueberry filling and drip some off the sides (optional). Decorate with oreos and/or fresh blueberries. Enjoy!
    5 oreo cookies, ¼ cup fresh blueberries

Video

Notes

The cake will keep well in the fridge for up to 3 days. Store it in a cake carrier to protect it and keep it fresh. To freeze the cake, pop the cake in the freezer for a few hours to firm up the frosting. Wrap it up tightly and freeze for up to 2 months. You can also freeze individual slices.
Make sure to let the cake sit at room temperature for 15-20 minutes if refrigerated. This will help it soften (because of the butter) and give you the best cake experience.
Tip: This cake has a very subtle lemon flavour that helps enhance the blueberry flavour. To make this cake have more lemon flavour, add an extra tablespoon of grated lemon zest to the cake layers and one tablespoon to the blueberry filling right before taking it off the heat.
If you don't like lemon, omit the zest from the cake layers. Do NOT omit the lemon juice - you need the acidity. Lemon juice won't make the cake taste like lemon.