Preheat the oven to 350°F. Grease three 8-inch round pans and line the bottoms with parchment paper. Set aside.
With a hand mixer in a large bowl, or in the bowl of a stand mixer using the paddle attachment, cream together the butter, sugars and lemon zest on medium high speed until fluffy and light . This step is important to get a good rise and texture for your cake! Let it mix for at least 4-5 minutes!
Add the eggs one at a time, beating to make sure the first is incorporated before adding the next. Once all of the eggs are added, add in the vanilla and let it all mix for 1-2 minutes, until totally combined. Scrape down the sides of the bowl if you need to.
In a separate, medium-sized bowl, add the flour, baking powder, soda and salt. Whisk together until homogeneous.
Alternating wet and dry, add 1/3 of the dry ingredients to the batter until just a few flour streaks remain, then add in 1/2 of the buttermilk and lemon juice. Repeat until you run out of ingredients to add. You should have done three additions of dry and two additions of wet, starting and ending on the dry ingredients.
In a small bowl, toss the blueberries with the three tablespoons of flour. Add the blueberries to the batter and fold gently with a spatula until evenly distributed.
Evenly distribute the batter between your three cake pans and bake for 30-35 minutes or until a toothpick inserted in the center comes out clean. Remove from oven and allow to cool completely before removing the cakes from their pans.