In a large bowl, using an electric mixer beat the butter on medium-high until creamy, this will take about 1 minute.
Next, add granulated sugar and beat until light and fluffy, about 3 minutes.
Add the eggs one at a time, beating after each addition, and after that add the vanilla. Scrape down the sides and bottom of the bowl as needed.
In a large bowl, whisk together the flour, baking powder, and salt.
Now, slowly add the flour mixture to the butter mixture, with the mixture on low speed. Finally, beat in the buttermilk, lemon zest, and lemon juice just until combined.
Using a spatula, in a medium bowl toss the blueberries with 1 tablespoon of flour or cornstarch and gently fold them into the batter.
The cake batter will be very thick, make sure to not over-mix it.