Preheat your oven to 350°F (175°C). Lightly grease and flour a 9x13 inch baking pan, or line it with parchment paper for easy removal.

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until the mixture is light and fluffy, about 2-3 minutes.

Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract, lemon zest, and fresh lemon juice.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Begin and end with the dry ingredients. Mix until just combined; be careful not to overmix.

Gently fold in the fresh blueberries that have been tossed with a tablespoon of flour. This helps prevent them from sinking to the bottom of the cake.

Pour the cake batter into the prepared baking pan and spread it evenly. Bake for 30-35 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan on a wire rack for 10-15 minutes, then carefully invert it onto the wire rack to cool completely before frosting.

While the cake cools, prepare the frosting. In a large bowl, beat the softened cream cheese and butter together with an electric mixer until smooth and creamy.

Gradually add the sifted powdered sugar, fresh lemon juice, lemon zest, vanilla extract, and a pinch of salt. Beat until the frosting is light and fluffy.

Once the cake is completely cool, spread the lemon cream cheese frosting evenly over the top. For a decorative touch, garnish with extra lemon zest or a few fresh blueberries, if desired.

Cut the cake into squares and serve. Enjoy!