Preheat the oven to 350° F and grease and flour a 10-inch bundt pan. (Grease the pan with a thin layer of shortening followed by a layer of flour, making sure to cover the pan well to avoid sticking.)
In a large bowl, whisk together the flour, baking powder, baking soda, and salt.
In a separate mixing bowl, beat the butter until smooth (3-4 min.). Add sugar and beat for 2-3 minutes until fluffy.
Beat eggs into the butter mixture one at a time, beating well after each addition. Add lemon juice, zest, vanilla, and sour cream. Mix until fully combined.
Mix in the flour mixture in 3 additions, alternating with the buttermilk. Mix just until ingredients are fully combined. Coat the blueberries in flour, and then gently fold them into the batter.
Pour the batter into a greased bundt pan and bake for 50-55 minutes. Let cool for 10-15 minutes, then flip the pan over onto a cooling rack, removing your cake from the pan.