Preparation Steps

• Preheat oven to 350°F. Grease two 8-inch round cake pans with butter and line the bottoms with parchment rounds.
• Make the blueberry filling: In a saucepan, combine 2 cups blueberries, 0.5 cup granulated sugar (from the divided amount), cornstarch, and lemon juice. Cook over medium heat, stirring, until bubbling and thickened, 4 to 6 minutes. Remove from heat and cool completely. Reserve the remaining 1 cup blueberries for assembly.
• Whisk the dry ingredients: In a bowl, whisk flour, baking powder, and salt until evenly combined.
• Cream butter and sugar: In a large bowl, beat softened butter with the remaining 1.25 cups granulated sugar until pale and fluffy, 2 to 3 minutes. Beat in eggs one at a time, then 2 teaspoons vanilla.
• Finish the batter: Mix sour cream into the milk. Add dry ingredients to the butter mixture in 3 additions, alternating with the milk mixture, beginning and ending with dry. Stir in lemon zest just until combined.
• Bake: Divide batter evenly between prepared pans and smooth tops. Bake 22 to 26 minutes, or until a toothpick in the center comes out clean. Cool in pans 10 minutes, then invert onto racks to cool completely.
• Make stabilized whipped cream: Beat softened cream cheese with powdered sugar and the remaining 1 teaspoon vanilla until smooth. With the mixer running, slowly stream in cold heavy cream and whip to stiff peaks.
• Assemble: Place one cake layer on a platter. Spread half the cooled blueberry filling to within 0.5 inch of the edge. Dollop and spread about one third of the whipped cream over the filling. Scatter half of the reserved fresh blueberries on top.
• Top with the second layer. Spread the remaining blueberry filling on top and mound with more whipped cream. Use the rest of the fresh blueberries to garnish. Sprinkle turbinado sugar on top if using.
• Chill 30 minutes to set the layers, then slice and serve.