Lemon Blueberry Layer Cake

Preheat the oven to 350°F and generously spray two 8- or 9-inch round cake pans (or you can do this with one cake pan, baking one at a time) with cooking spray. Using a stand mixer fitted with the paddle attachment (or a large mixing bowl with a hand mixer), combine the butter, sugar, egg whites and lemon juice and beat on medium speed until creamy and free of lumps.
In a separate bowl, combine the flour, baking powder and salt. Mix well. Gradually add to the butter mixture and beat on medium speed until just combined. Add the lemon zest and the milk gradually and mix until creamy. In a medium bowl, combine the blueberries and the 1 Tbsp flour. Mix so that blueberries are well coated and fold into the batter.
Divide the batter between the prepared cake pans and bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean. Let cool in pan for 5 minutes, remove from pan and let cool completely on a wire rack. Using a serrated bread knife, cut the rounded tops off each cooled cake. Remove the center from one of the cooled cakes using a round 3- or 4-inch cookie cutter.

Place the intact cake in the center of a cake or serving plate. Spread the frosting evenly and generously over the top in an even layer. Top with approximately 1/2 cup of the lemon curd and spread in an even layer, leaving a 1-inch margin around edge. Top with the cake that has the hole in the center. Fill the center hole with frosting.
Using an offset or icing spatula, apply frosting to the sides of the cake and create a smooth surface. Repeat on the top of the cake. Drizzle the remaining lemon curd over the cake and decorate with blueberries. Refrigerate until ready to serve.