This moist and easy blueberry cake is simple, yet SO delicious and makes the perfect Spring, Mother's Day, or anytime dessert! Top it off with a beautifully swirled frosting to take it to the next level (it's so much easier than you think!).
Preheat oven to 350 degrees. Grease and flour an 8 or 9-inch cake pan ( should be at least 2-inches tall).
Prepare the Blueberries
In a small bowl combine blueberries and lemon juice and stir to coat. Sprinkle flour over the blueberries, stir gently to coat in the flour. Set aside.
Prepare the Cake
In a medium bowl whisk together flour, baking powder, salt, and cinnamon.
In a large bowl, combine butter and sugar and mix 2-3 minutes until light and fluffy. Mix in eggs and vanilla. Mix in the lemon zest now, if using.
Add dry ingredients to wet ingredients and mix until just combined (do not over-mix). Gently stir in blueberries.
Transfer cake batter (it is thick) to your prepared cake pan using a greased rubber spatula to gently smooth out evenly.
Transfer pan to preheated oven and bake for 45 minutes or until a toothpick inserted in the center comes out clean (no wet batter).
Allow to cool for 10-15 minutes before turning cake out onto a cooling rack to cool completely. Meanwhile, prepare the frosting.
Make the Frosting
In a blender or food processor (I used an immersion blender) puree the blueberries. Use a fine mesh strainer to strain the blueberry skins. Discard the skins and set aside the blueberry puree.
In a large bowl cream the butter for 3 minutes (don't skimp on the time here!).
Cream in the powdered sugar 1/2 cup at a time until completely incorporated.
Mix in the vanilla, salt, and lemon zest (if using).
Portion out half of the frosting into a separate bowl. To the first bowl add your blueberry puree and mix until combined. If desired you can add some food coloring to enhance the purple color. (I used a combination of blue and red to achieve the color in my photos. You can also use purple if you have it on hand).
To the second bowl of frosting, add the heavy cream 1 tablespoon at a time until frosting is fluffy.
Frost the Cake
Drop dollops of each frosting onto the top of the cooled cake (*make sure it is completely cooled before frosting*). Gently swirl and the frostings together as you spread it evenly across and down the sides of the entire cake.
Slice and serve OR store in airtight container at room temperature for 1 day or in the fridge up to 5 days.
There are two steps you don't want to skip with the blueberries, and that's mixing them with lemon juice and then rolling them in flour. This helps keep them from sinking right down to the bottom of the cake. The other step is removing the blueberry skins from the frosting puree. You want a nice, smooth frosting, not one littered with little skins you'll be picking out of your teeth all night.
If you have any leftover buttercream frosting, it will keep in the fridge for up to 5 days. You might need to give it a stir before using.
If you want to skip the zest that's totally fine. Don't make up for it by using more juice. Keep the lemon juice for mixing with the berries and the zest for the inside of the blueberry cake with lemon and the frosting.