Preheat oven to 350°F (175°C) and grease a 9-inch bundt pan or deep loaf pan with butter and flour.

Whisk together 2 1/2 cups flour, baking powder, and salt in a medium mixing bowl.

In a stand mixer, cream the butter and granulated sugar on medium-high speed until light and fluffy, about 3-5 minutes.

Add eggs one at a time, beating well after each addition, then stir in the lemon zest, lemon juice, and vanilla extract.

Reduce mixer speed to low and add the dry ingredients in three parts, alternating with the buttermilk in two parts, beginning and ending with the flour mixture.

In a small bowl, toss the blueberries with 1 tablespoon of flour until coated, then gently fold them into the batter by hand.

Transfer the batter to the prepared pan and smooth the surface with a spatula.

Bake for 55 to 60 minutes, or until a skewer inserted into the thickest part of the cake comes out clean.

Cool the cake in the pan for 10 minutes before inverting onto a wire rack to cool completely before glazing.