Preheat the oven to 350 degrees F (175 degrees C). Lightly butter and sugar three 8-inch round nonstick cake pans.

Sift flour, baking powder, baking soda, and salt together in a medium mixing bowl.

Cream sugar and butter together in a large bowl using an electric mixer. Mix in lemon juice until smooth. Add eggs 1 at a time, mixing until fully combined. Alternate adding the flour mixture and buttermilk with the mixer set to the lowest speed. Mix until batter is smooth, scraping the bowl down occasionally. Use a spatula to gently fold in blueberries.

Fill the prepared cake pans evenly with batter.

Bake in the preheated oven until a toothpick inserted into the center of each cake comes out clean, 30 to 35 minutes. Let cool completely before removing from the pans, about 30 minutes.

While cakes are cooling, beat butter for frosting in a large mixing bowl using an electric mixer on medium speed. Reduce speed to low and add confectioners' sugar a little at a time, alternating with splashes of milk and vanilla extract. Mix until frosting is smooth.

Spread frosting over each of the cooled cake layers and stack; then frost the sides.