Preheat the oven to 325°F. Place a large roasting pan on the lower third rack of the oven. Place a kettle of water on the stove to boil. Spray a 9-inch springform pan with nonstick spray and line the bottom with a round of parchment paper. Wrap a double layer of foil around the bottom and up the sides of the pan (you want to seal it so the water from the water bath doesn't seep into the pan). In a large bowl, use an electric mixer to mix the cream cheese- blend until it is nice and smooth and creamy. Mix in sugar and salt and blend for 2 minutes, scraping down sides of the bowl as needed. Add eggs, one at a time, blending after each addition. Finally, mix in sour cream, whipping cream and vanilla. Mix until smooth. Pour the batter into the prepared pan. Set the pan into the roasting pan in the pre-heated oven. Carefully pour the hot water from your kettle into the roasting pan (it will fill the pan surrounding the cheesecake). Pour enough water so that there is about an inch of water coming up the foil along the sides of the cheesecake pan. Bake the cheesecake for 45 minutes. It should be set to the touch and not jiggly. Remove the cheesecake from the roasting pan and let it cool on a wire rack for at least an hour. When it has cooled, place the pan into the freezer and let the cheesecake freeze completely. This can be done in several hours- or overnight.
PREPARE THE CAKE LAYERS:
Preheat the oven to 350°F. Spray two 9-inch round pans with baking spray.
In a large bowl, use a mixer to beat the butter on medium-speed until creamy, about 1 minute. Gradually add the sugar, beating until light and fluffy, about 4 minutes. Add the eggs, 1 at a time, beating just until blended after each addition.
In a medium bowl, whisk together the flour, baking powder, salt and baking soda. Gradually beat in the dry ingredients into the wet ingredients, alternately with the buttermilk, beginning and ending with the flour mixture. Stir in the lemon zest, lemon juice and vanilla. Toss the blueberries with the tablespoon of flour. Gently fold the blueberry/flour mixture into the batter. Divide the batter between the two pans.
Bake for 23 to 25 minutes, or until a toothpick inserted into the center comes out clean. Cool on wire racks for 10 minutes, the remove the cakes to the wire racks and let them cool completely.
PREPARE THE FROSTING:
In a large bowl, using an electric mixer on medium-high speed, beat powdered sugar, cream cheese, butter and vanilla until it is smooth and creamy (do not over beat).
ASSEMBLE THE CAKE:
Place one cake layer into the center of a cake plate or platter. Remove the cheesecake from the freezer, take off the sides of the pan, and slide a knife under the parchment to remove the cheesecake from the pan. Peel off the parchment. Measure your cheesecake layer against the cake layers. If the cheesecake layer turns out to be a slightly larger round than your cake, move it to a cutting board and gently shave off some of the exterior of the cheesecake to get it to the same size as your cake layers. Place the cheesecake layer on top of the first cake layer. Place the 2nd cake layer on top of the cheesecake.
FROST THE CAKE, AND SERVE:
Apply a crumb coat layer to the cake- use a long, thin spatula to cover the cake completely with a thin and even layer of frosting. Be sure to wipe off your spatula each time you are about to dip it back into the bowl to get more frosting (this way you won't be transferring any red crumbs into the bowl of frosting). Don't worry at this point about the crumbs being visible in the frosting on the cake. When your cake has a thin layer of frosting all over it, place it into the refrigerator for 30 minutes to "set" the frosting. Once the first layer of frosting is set, apply the 2nd layer. Start by adding a large scoop of frosting onto the top of the cake. Use a long, thin spatula to spread the frosting evenly across the top and then spread it down the sides of the cake too. Because you applied a crumb-coat layer, you shouldn't have any crumbs floating around in the final frosting layer. Decorate, as desired. I recommend piping a little more frosting decoratively on top. Sprinkle on some fresh blueberries and lemon zest. Perhaps mint leaves too. Keep this cake refrigerated until ready to serve.