Preheat oven to 350° F. Spray a 8 1/2 x 4 1/2 loaf pan with cooking spray and set aside.
In a large bowl, whisk together the flour, salt, and baking powder. In a small bowl, combine sugar and lemon zest. Rub together with your fingers until fragrant. Whisk into the flour mixture. Set aside.
In a separate medium bowl, combine the buttermilk, oil, eggs, lemon juice and vanilla extract.
Slowly add the wet ingredients to the dry ingredients. Stir until combined. Gently stir in the blueberries. Pour batter into prepared loaf pan. Pound on the counter so the loaf cake is evenly set in the pan.
Bake for 60-70 minutes, or until toothpick comes out clean. Place the loaf on a cooling rack and cool for 15 minutes. Loosen the sides of the loaf cake with a knife. Carefully remove loaf from pan. Let cool completely on wire rack.
While the loaf cake is cooling, make the lemon glaze. In a small bowl, whisk together powdered sugar and lemon juice. Drizzle the glaze of the cooled loaf cake. Cut into slices and serve.
Note-if the cake isn't done and the top is browning too much, drape a piece of aluminum foil over the top and finish baking until a toothpick comes out clean.