I had sooooo much fun making this cake! It was simply a product of my trying to use up any extra food I had around the kitchen before my move back to Germany. My decision to move back to Germany was kind of rash. It just so happened that I had gone shopping to stock up on baking supplies just a week before the big decision hit. So I was kind of left with an overabundance of all types of sugar, flour, chocolate chips, etc. I mean, seriously, how am I supposed to use up six 2 lb bags of confectioner’s sugar in two weeks??? That seems impossible even for me. So anyways! That’s how this cake came about.
What to do with 6 cups of frozen blueberries, 2 frozen round cake layers, and an excessive amount of butter and confectionary sugar? Why, Lemon-Blueberry Layer Cake of course! Or at least that’s where my mind went haha I love a good layer cake and I’ve never made a cake with a fruit filling before so, why not? My frozen cake layers were leftover from my Wilton Cake Decorating courses. They were actually meant to be for the last class’ “project cake”, but I was going to end up missing that class since I would be on vacation in GA. SO! I decided to do my own thing with them. Considering the amount of butter that I had laying around, I also thought that a traditional lemon buttercream would be the way to go rather than the Wilton Class’ buttercream (made with shortening- yuck!). That’s how this cake was born.
The blueberry jam recipe is quick and simple, but should be prepared WAY in advance so that it has a chance to cool and thicken entirely. Doing that will make it so much easier to sandwich between layers without it oozing every where (a lesson I learned very quickly…). Since my blueberries were frozen I added a bit of water to get things going and I ended up with a much soupier jam than anticipated, so I added a bit of thickener. If your berries are fresh, you shouldn’t have to do that. OR if you feel so inclined, you may use a store-bought blueberry jam. Whatever works for you.
I used my favorite white cake recipe for the cake layers. Since they were pre-made, the flavor was vanilla, not lemon. If I were to do this again from scratch I would probably add a tablespoon of lemon zest to the cake batter, by rubbing it into the sugar before mixing. AND I would take a tablespoon or two of the jam and swirl it into the batter once poured into the pans. All these things are completely optional and not written out in the recipe since I wanted to keep it pretty simple, but wow, would it make for one over-the-top-awesome-cake!
The buttercream couldn’t be simpler- 4 sticks butter, 2 lb bag confectioners’ sugar, 1 Tb lemon juice, and 1 tsp lemon extract. Plus extra milk as needed. Very basic. I made A LOT for this recipe since I planned on piping on it. Feel free to scale it back if you think it’s necessary. I always feel safer with more frosting rather than less and having to skimp somewhere while frosting.
Just a word to the wise- if you have never used a jam filling between cake layers before, be careful! I spread a thin layer of buttercream on the top of one layer and the bottom of another, then piped a border along the edge of the cake with buttercream on top. The thin layers of buttercream help to prevent the jam from soaking into the cake layers. Make sure you bring the border in a 1/4″ or so, at least. My first time, I put it right along the edge and once I placed a cake layer on top, its weight pushed the frosting border out and let a ton of jam escape. It was quite messy… So make sure you take that into account and you should be fine. And of course, be sure your jam is cooled and thick! (You can see the lesson learned very clearly in the second photo haha)
In the end I was left with one of the best cakes I’ve ever made. And from scraps! I couldn’t believe it. Things did get really messy when jam leaked everywhere and kept coming out of the frosting I was piling around the sides… but at that point I just put the whole thing in the fridge and waited until the next day to worry about it. I covered the mess with some leftover frosting, evened the sides up a bit, and nobody even noticed the terrible trouble I had! I was VERY happy with this cake : )
- For the Blueberry Jam:
- 1 lb blueberries (about 2½ cups)
- ½ cup sugar
- For the White Cake:
- ½ cup (1 stick) butter, room temperature
- 1½ cups sugar
- 4 egg whites, room temperature
- 2 tsp vanilla extract
- 2 cups flour
- 1 tsp baking powder
- ½ tsp baking soda
- ¼ tsp salt
- 1⅓ cups buttermilk, room temperature
- For the Lemon Buttercream:
- 2 cups (4 sticks or 1 lb) unsalted butter, room temperature
- 2 lb confectioners' sugar, sifted (8 cups)
- 1 Tb fresh lemon juice
- 1 tsp lemon extract
- 1 to 2 Tb milk to reach desired consistency if needed
- For the Jam: Heat all ingredients together over med-low heat, allowing the berries to burst. Simmer on low until well thickened, about 15 minutes. Cool completely in the refrigerator.
- For the Cake: Preheat oven to 350°F and prep two 8" round cake pans. Cream together butter and sugar until light and fluffy, about 3-4 minutes. Add egg whites, one at a time, beating well after each addition. Mix in vanilla.
- In a medium bowl, sift together flour, baking powder, baking soda, and salt. Whisk to evenly combine. Add to the creamed mixture alternately with the buttermilk (beginning and ending with the flour), beating well after each addition.
- Evenly fill cake pans and bake 30-35 minutes or until a toothpick inserted in the center comes out clean. Let cool in pan for 10 minutes then remove to a wire rack to cool completely.
- For the Buttercream: Beat together butter until smooth. Add remaining ingredients, mixing on low until well combined. Add milk as needed for desired consistency.
- To Assemble: Cut cake layers each in two, if desired. Frost the top of one cake layer with thin layer of frosting. Do the same with the bottom of the another layer. Pipe a border around bottom layer at least ¼" in from the edge. Fill the inside of the border with jam, no more than ¼ cup (Eyeball it. It will spread!) Gently top with cake round, frosted layer side down. Repeat with remaining cake layers, if using. Frost with buttercream.