1-Preparing the Cake Batter: First, get your pans ready: butter and flour three 6-inch round pans, and if you have them, add damp fabric strips around the edges for even rising. In a bowl, whisk together the wet ingredients ½ cup whole milk, ½ cup sour cream, 3 egg whites, 3 tablespoons fresh lemon juice, 1 tablespoon lemon zest, and 1 tablespoon vanilla extract until well combined. For more for essential baking techniques on mixing, check out our guide. Then, sift the dry ingredients: 2 cups all-purpose flour, 1⅔ cups granulated sugar, 1½ teaspoons baking powder, and ¼ teaspoon kosher salt, but save 1 tablespoon of flour to coat the blueberries later.

2-Making the Blueberry Reduction: Next, freeze ½ cup of blueberries for decoration. In a saucepan, cook the remaining 1½ cups fresh blueberries with 1 tablespoon granulated sugar, 1 tablespoon fresh lemon juice, and 1 tablespoon water over medium-low heat until the berries burst and the mixture reduces by half. Strain it and let it chill in the fridge; this adds a burst of flavor that’s worth the extra step.

3-Whipping Up the Buttercream and Assembling: For the lemon buttercream, beat 1½ cups unsalted butter and ¼ teaspoon kosher salt until fluffy, then gradually add 6 cups confectioners’ sugar and 3 tablespoons fresh lemon juice, one tablespoon at a time. Mix about 1 cup of this frosting with the chilled blueberry reduction to create a blueberry version. To assemble, pipe a ring of lemon buttercream on each cake layer’s edge, fill the center with blueberry buttercream, and stack them. Frost the outside with lemon buttercream, add dollops near the edge, and decorate with the frozen blueberries. Chill for 20 minutes before slicing for the best results.