Preheat and Prepare the Pan

Preheat your oven to 350°F (175°C).

Grease a 9×13-inch baking dish and line it with parchment paper, leaving an overhang on the long sides for easy removal later.

Mix Dry Ingredients

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

Cream Butter and Sugar

In a stand mixer fitted with the paddle attachment (or using a hand mixer), cream together the butter and granulated sugar on medium speed until light and fluffy—about 3–4 minutes.

Add Wet Ingredients

Add the eggs, one at a time, mixing well after each addition.

Pour in the vanilla extract, then add the buttermilk, mixing on low speed until just combined.

Mix in the lemon juice and zest.

Combine Dry and Wet

Gradually add the dry ingredients into the wet ingredients and mix until no streaks of flour remain.

Gently fold in the blueberries tossed in flour with a spatula, being careful not to overmix.

Bake

Pour the batter into the prepared pan and smooth out the top.

Bake for 40–45 minutes, or until a toothpick inserted into the center comes out with moist crumbs.

Let the cake cool completely in the pan on a wire rack.

Glaze

In a small bowl, whisk together the powdered sugar and lemon juice until smooth and pourable.

Pour the glaze over the cooled cake and spread it evenly.

Allow the glaze to set completely before slicing and serving.