Preheat oven to 350-degrees.
Grease and flour 2 large metal loaf pans (10”x 5”x 3”) or spray with cooking spray then line the pans with a sheet of parchment paper.
Beat the butter on medium speed until creamy, about 1 to 2 minutes.
Slowly pour in the sugar and continue beating until well combined and fluffy, about 2 minutes.
Add the eggs one at a time, mixing each into the butter and sugar on medium speed for about 30 seconds. After all the eggs have been added continue beating for about 2 minutes, until the mixture is very light and fluffed.
In a small bowl whisk 4-½ cups of the flour with the kosher salt and the baking powder.
Scoop about ¼ of the flour into the batter blending in using low-speed just until the flour disappears. Alternate with the milk, beginning and ending with the flour. Don’t over mix or the bread will be tough.
Pour in the lemon and vanilla extracts along with the lemon zest and lemon juice.
Toss the the blueberries with the remaining 2 teaspoons of flour, lightly coating the blueberries.
Using a spatula, gently fold in the blueberries taking care not to break the berries.
Divide the batter between the prepared loaf pans and sprinkle the remaining teaspoon of sugar over the top.
Bake in a 350-degree oven for 50 to 60 minutes or until the bread tests done with a toothpick inserted into the center of the loaf.
Cool the bread in the pan on a rack for 10 minutes then remove and finish cooling on a wire rack.