Prepare the Blueberry Puree:

1. Puree 1 1/2 cups of blueberries in a blender or food processor.
2. Transfer the puree to a saucepan with 1/4 cup of water and cook over medium heat until reduced to 3/4 cup.
3. Let the puree cool completely before using.

2. Mix the Cake Batter:

1. Preheat oven to 350°F (175°C). Grease and flour three 8-inch round cake pans.
2. In a medium bowl, whisk together cake flour, baking powder, baking soda, and salt.
3. In a separate bowl, mix sour cream, cooled blueberry puree, and vegetable oil.
4. In a stand mixer, cream the softened butter and sugar until light and fluffy, about 3-4 minutes.
5. Add eggs one at a time, beating well after each addition.
6. Alternate adding the dry ingredients and wet mixture to the butter mixture, beginning and ending with the dry ingredients. Add pink gel coloring if desired.
7. Gently fold in the whole blueberries.

3. Bake the Cake Layers:

1. Divide the batter evenly among the prepared pans.
2. Bake for 22-25 minutes, or until a toothpick inserted into the center comes out clean.
3. Let the cakes cool in their pans for 10 minutes, then turn them out onto cooling racks to cool completely.

4. Make the Lemon Cream Cheese Frosting:

1. In a stand mixer, beat the softened butter until smooth.
2. Add the cream cheese and mix until fully combined.
3. Gradually add powdered sugar, lemon juice, and lemon zest. Beat until the frosting is smooth and creamy.

5. Assemble the Cake:

1. Place one cake layer on a serving plate or cake stand. Spread a generous layer of frosting over the top.
2. Repeat with the second and third layers, spreading frosting evenly between each.
3. Frost the top and sides of the cake with the remaining frosting.

6. Decorate and Serve:

1. Garnish the cake with additional blueberries and lemon slices for a vibrant finish.
2. Chill the cake for 30 minutes before slicing to ensure clean cuts.