Blueberry Cheesecake: Preheat your oven to 350°F. Lightly grease an 8-inch springform pan and line the bottom with parchment paper. Wrap the outside of the pan with a double layer of heavy-duty aluminum foil to prevent water from seeping in during baking in a water bath. To prepare the cheesecake, pulse the blueberries and cream cheese together in a food processor until smooth, then transfer to a mixing bowl. Add sugar and flour, beating until smooth and creamy, then stir in the vanilla. Add the eggs one at a time, mixing just until combined after each addition—be careful not to overmix. Finally, fold in the sour cream and heavy cream. Pour the batter into the prepared springform pan, smoothing the top, then place the pan inside a roasting pan. Pour boiling water into the roasting pan until it reaches halfway up the sides of the springform pan, making sure no water splashes into the batter. Bake for 40-45 minutes or until the center is set. Remove the springform pan from the water bath, run a thin knife around the edges to loosen, and allow it to cool to room temperature. Then refrigerate for several hours or overnight to chill completely.

Lemon Blueberry Cake: Preheat the oven to 350°F. Butter and lightly flour two 8-inch round cake pans, then line the bottoms with parchment paper circles. In a bowl, sift together the flour, cornstarch, baking powder, and salt; set aside. In a separate bowl, combine the milk and lemon juice and let it curdle. In a stand mixer, beat the butter and sugar on medium-high speed until pale and fluffy, about 4 minutes. With the mixer on low, add the eggs one at a time, mixing well after each addition. Add the vanilla extract and lemon zest, mixing to combine. Begin incorporating the dry and wet ingredients alternately, starting with one-third of the flour mixture, then half the milk mixture, followed by another third of the flour mixture, the remaining milk, and finally the last of the flour mixture. Mix gently after each addition, being careful not to overmix. Toss the blueberries with flour in a small bowl to coat them, then fold them gently into the batter to avoid breaking the berries. Divide the batter evenly between the prepared pans, smooth the tops, and bake for 30-35 minutes or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10-15 minutes before transferring them to a wire rack to cool completely.

Cream Cheese Frosting: In a mixing bowl, beat the butter and cream cheese on medium speed until smooth and lump-free. Avoid overbeating before adding sugar to prevent a runny texture. Add vanilla extract, salt, and lemon zest, mixing until combined. Gradually add powdered sugar until you reach your desired sweetness and thickness, scraping down the bowl’s sides and beating until the frosting is smooth.

Assembling the Cake: Place one cake layer on a serving plate and spread a thin layer of lemon cream cheese frosting over the top. Add the blueberry cheesecake layer and cover it with another thin layer of frosting. Top with the second cake layer and frost the entire cake with the remaining frosting. Decorate with lemon wedges and fresh blueberries if desired. Refrigerate the cake for at least 45 minutes before slicing to ensure it holds together well. Store the finished cake in the refrigerator.