01 - Preheat oven to 350°F. Grease and line two 8-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
03 - In a large bowl, beat butter, oil, and sugar until light and fluffy, approximately 3 minutes. Add eggs one at a time, beating well after each addition.
04 - Mix in lemon zest, lemon juice, and vanilla extract into the creamed mixture.
05 - Add dry ingredients to wet mixture in three parts, alternating with buttermilk. Begin and end with flour mixture. Mix until just combined.
06 - Toss blueberries with 1 tablespoon flour, then gently fold into the batter.
07 - Divide batter evenly between prepared pans and smooth the tops.
08 - Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Cool cakes in pans for 10 minutes.
09 - Turn cakes out onto a wire rack and allow to cool completely.
10 - Beat cream cheese and butter together until smooth and creamy. Add powdered sugar gradually, then mix in lemon zest, lemon juice, vanilla, and salt. Beat until fluffy.
11 - Spread a layer of frosting between the cooled cake layers, then frost the top and sides. Decorate with fresh blueberries and additional lemon zest if desired.