You have never seen a beautiful and equally delicious cake as this lemon blueberry cake! Elegant, delicious, and fit for any occasion, this cake will knock your socks off!
Preheat the oven to 350°. Grease 2 8 inch round cake pans and set aside.
In a small bowl combine the sugar with the zest of the lemons until fragrant.
In a large bowl whisk together the lemon sugar, 2 cups of the flour, baking powder, baking soda, and salt.
To the same bowl add the buttermilk, lemon juice, vanilla, and oil and beat with the paddle attachment of a stand mixer or a hand mixer just until fully combined.
In another bowl whip the egg whites until medium stiff peaks form. Fold ⅓ of the egg whites into the cake batter to loosen it up, followed by the remaining egg whites. Fold until only a few streaks of egg whites remain.
Toss the blueberries with the remaining ¼ cup of flour. Fold into the cake batter until just combined.
Separate the cake batter evenly into the two cake pans and bake for about 30-35 minutes, until a toothpick comes out clean and the center of the cake springs back when lightly pressed. Let cool completely before frosting.
Filling
In a small bowl, combine the blueberry jam with the lemon zest. Refrigerate until ready to use.
Whipped Lemon Frosting
Place the soft butter into the bowl of a mixer and use the paddle attachment to beat the butter for about 3 minutes, until it’s a pale-yellow color.
Add the powdered sugar and mix on low until it has been incorporated. Add the lemon zest, vanilla, and 3 tablespoons of cream. Beat on medium-high for about 3 minutes, until light and fluffy. Scrape down the sides and bottom of the bowl with a rubber spatula as needed.
For a softer frosting, add more cream 1 tablespoon at a time until the frosting is the desired thickness. For this cake, I recommend keeping the frosting stiff enough to form thick peaks to frost the cake.
Assembly
Place one cake round top down on the plate or cake stand.
Use a piping bag with a large round or star tip to pipe a dam around the edge of the cake to prevent the filling from coming out the sides. Fill the center of the well with the blueberry jam filling.
Place the second cake round on top of the first, top down. Use the piping bag to pipe frosting all around the outside and top of the cake. Use an offset spatula to smooth the frosting. Top with fresh blueberries and slices of fresh lemon.