Preheat the oven to 350°F (180°C). Grease and flour a 9x13 inch cake pan.

In a medium bowl, sift together the cake flour, baking powder, baking soda, and salt. Whisk together and set aside.

In another bowl, combine the buttermilk and freshly squeezed lemon juice. Whisk with a fork and set aside.

In a large bowl, beat together the softened butter, sugar, and lemon zest until it’s fluffy and light, about 2-3 minutes.

Add the vanilla extract and then the eggs, one by one, mixing well and scraping down the sides of the bowl after each addition.

With the mixer on low speed, alternate adding 1/3 of the flour mixture and half of the buttermilk mixture, mixing until just combined. Repeat until everything is in the bowl—make sure not to overmix!

Toss the blueberries with 2 teaspoons of flour. Fold them gently into the batter.

Pour the batter into your prepared pan and bake for 30-35 minutes for a 9x13 inch pan, or 25-30 minutes for layered cakes.

Let the cakes cool in the pan, handling with care if making a layer cake.

In a medium bowl, beat the softened butter and cream cheese until smooth.

Add the lemon juice and then gradually mix in the powdered sugar, adjusting the consistency with a bit of whipping cream as needed.

Frost the cooled cake.