Preheat the oven to 350°F (175°C). Grease and line two 9-inch round cake pans with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large mixing bowl, beat the butter and sugar until light and fluffy, about 3–4 minutes. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Add the dry ingredients in three additions, alternating with the buttermilk, mixing just until combined. Toss the blueberries with 1 tablespoon of flour, then gently fold them into the batter.
Divide the batter evenly between the prepared cake pans and bake for 28–32 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.
Meanwhile, prepare the cheesecake layer. Beat the cream cheese until smooth. Add the sugar, egg, vanilla, and sour cream, mixing until creamy. Pour the mixture into a parchment-lined 9-inch round pan and bake at 325°F (160°C) for 30–35 minutes. Allow the cheesecake to cool completely, then refrigerate for at least 2 hours.
For the blueberry filling, combine the blueberries, sugar, and lemon juice in a small saucepan over medium heat. Cook until the berries begin to soften. Stir together the cornstarch and water, then add to the saucepan. Continue cooking until thickened, then cool completely.
To prepare the frosting, beat the cream cheese and butter until smooth. Gradually mix in the powdered sugar, vanilla, and a pinch of salt until light and fluffy.