Preheat the Oven:
Preheat your oven to 350°F (175°C). Grease and flour a 9x9-inch or 9x13-inch baking dish.
Prepare the Blueberry Bar Batter:
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large mixing bowl, cream the softened butter and sugar together until light and fluffy, about 3-4 minutes with an electric mixer.
Beat in the eggs one at a time, then add the vanilla extract and lemon zest.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Mix until just combined.
Gently fold in the blueberries using a spatula, being careful not to crush them.
Bake the Bars:
Pour the batter into the prepared baking dish, spreading it evenly.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Let the bars cool in the baking dish for about 10-15 minutes before transferring them to a cooling rack to cool completely.
Prepare the Lemon Glaze:
In a small bowl, whisk together the powdered sugar, lemon juice, and lemon zest until smooth and well combined.
Drizzle the Lemon Glaze:
Once the bars are completely cooled, drizzle the lemon glaze over the top of the bars using a spoon or a small whisk.
Serve:
Slice the bars into squares and serve immediately. Enjoy with a cup of tea or coffee!