Start by preheating your oven to 350°F (180°C). Grease your 9x13 inch baking pan with butter or cooking spray, and if you like, lightly dust it with flour or line it with parchment paper to make cleanup a breeze.

Sift the cake flour, baking powder, baking soda, and salt in a medium bowl and mix them well. Whisk well to ensure a smooth mixture. Stir together the buttermilk and lemon juice in a separate bowl, then put it aside.

In a large bowl, beat together the softened butter and granulated sugar for about 2 to 3 minutes, until the texture is airy and pale. Add the lemon zest and enjoy that wonderful citrus scent filling the air.

Next, stir in the vanilla extract until fully blended. Then, add your eggs one by one, making sure to scrape down the sides of the bowl after each egg so everything mixes perfectly.

Let’s bring together the dry and wet ingredients! Start by adding 1/3 of the flour mixture to your batter. Mix gently on low until everything is barely combined. Then, pour in half of the buttermilk and lemon juice mixture, and stir to combine.

Scrape the bowl clean, then continue by adding another third of the flour mixture and followed with the rest of the buttermilk blend. Finish with the remaining flour. Be careful not to overmix, just combine everything until smooth and lump-free.

Dust your fresh blueberries with a bit of flour to keep them from settling at the bottom during baking. Gently fold them into the batter with a spatula, taking care not to break them up.

Place the batter into the prepared pan and evenly spread it with a spatula. Bake for 30-35 minutes, or until the surface is golden and firm. To check if it's ready, insert a toothpick into the center and make sure it comes out clean.

Once baked, set the cake aside to cool completely in the pan. Patience here is key; this ensures the frosting won’t melt off when you spread it on.

While the cake cools, prepare your frosting. Beat the softened butter until silky, then add the cream cheese and mix until everything is combined.

Add the lemon juice first, followed by a slow incorporation of the powdered sugar. Start on a low speed to avoid sugar clouds and then increase the speed to medium until the frosting is creamy and smooth. If it's too thick, add a little whipping cream to adjust the consistency.

When fully cooled, cover the cake with a rich layer of cream cheese frosting from edge to edge. Top it off with fresh blueberries for a beautiful final flourish.

Slice the cake into squares and get ready to enjoy the perfect balance of tangy lemon and juicy blueberries in every bite!