Step 1

Preheat the oven to 350 degrees F.

Step 2

Grease an 8-inch square baking pan.

Step 3

Line the greased pan with parchment paper.

Step 4

Reserve 1 tablespoon of the sugar, and then, using a stand mixer or a hand-held mixer, cream the remaining sugar, the butter, and the lemon zest together, until light and fluffy.

Step 5

Add the egg and the vanilla to the butter mixture and beat until combined.

Step 6

In a small bowl, toss the blueberries with 1/4 cup of the flour.

Step 7

In another bowl, whisk the remaining flour, the baking powder, and the salt together until thoroughly combined.

Step 8

Add 1/2 of the dry ingredients mixture to the batter and stir with a spatula to incorporate.

Step 9

Add the buttermilk and stir.

Step 10

Add the remaining dry ingredients mixture, stirring until the flour is absorbed.

Step 11

Fold in the blueberries, leaving any excess flour in the small blueberry bowl.

Step 12

Spread the batter into the prepared pan.

Step 13

Sprinkle the top of the batter with the reserved 1 tablespoon of sugar.

Step 14

Bake until a toothpick inserted into the center comes out clean, about 35-45 minutes.

Step 15

Let cool for 15 minutes.

Step 16

Serve.