Preheat oven to 350°F.
Prepare 9x4 bread pan by spraying with non-stick cooking spray or lining with parchment paper.
In a bowl, mix flour, baking powder and salt.
In a medium mixing bowl, beat together butter and sugar.
Beat eggs into the butter and sugar mixture.
Then buttermilk, lemon juice, lemon zest, and vanilla extract to wet ingredients.
In another bowl, toss blueberries with flour.
Add wet ingredients to dry ingredients and carefully fold together until nearly combined.
Add blueberries and stir until just combined. Do not overmix.
Pour batter into pan.
Bake for 45-55 minutes, or until a toothpick is pushed into the middle of the bread and comes out with bread crumbs, not wet batter.
Remove from oven, let cool for 10 minutes then remove bread from loaf pan and cool on a cooling rack.
Mix powdered sugar and lemon juice.
When bread is completely cool, pour lemon glaze over the top. Let set then slice and and serve.