Preheat oven to 350°F. Generously grease a bundt pan, making sure to coat every groove so the cake releases cleanly.
Whisk together the flour, baking powder, baking soda and salt in a medium bowl. Set aside.
Beat the softened butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each. Mix in the sour cream, milk, lemon juice, lemon zest and vanilla until smooth.
Gradually fold the dry ingredients into the wet mixture until just combined. Do not overmix.
Toss the blueberries with 1 tbsp of flour to keep them from sinking, then gently fold them into the batter.
Pour into the prepared pan and bake for 50 to 60 minutes until a toothpick comes out clean. Cover loosely with foil if the top browns too quickly.
Let the cake rest in the pan for 15 to 20 minutes then invert onto a wire rack to cool completely.
Whisk the powdered sugar, lemon juice, milk and vanilla until smooth and pourable. Drizzle generously over the cooled cake and let it run naturally down the sides.
