01 - Preheat oven to 350°F. Grease and flour two 9-inch round cake pans, lining bottoms with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt until thoroughly combined.
03 - Beat butter and sugar with an electric mixer on medium-high speed until light and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, mixing well after each addition. Incorporate lemon zest, lemon juice, and vanilla extract until fully blended.
05 - On low speed, alternately add flour mixture and buttermilk in three additions, beginning and ending with flour. Mix just until combined, being careful not to overmix.
06 - Toss blueberries with 1 tablespoon flour to prevent sinking. Gently fold coated berries into the batter by hand.
07 - Divide batter evenly between prepared pans. Smooth the tops. Bake for 30-35 minutes until a wooden toothpick inserted in the center emerges clean.
08 - Allow cakes to rest in pans for 10 minutes. Invert onto wire racks and let cool completely before frosting.
09 - Beat cream cheese and butter until smooth and creamy. Gradually incorporate powdered sugar, vanilla, lemon juice, and salt. Continue beating until fluffy and spreadable.
10 - Place one cooled cake layer on serving plate. Spread frosting evenly over top. Position second layer and frost top and sides. Garnish with additional blueberries and lemon zest if desired.