Begin by rinsing your fresh blueberries gently and patting them dry with a clean towel. Toss the berries in a small bowl with a teaspoon of flour; this will help suspend them in the batter during baking.

In a large mixing bowl, whisk together 2 cups of all-purpose flour, 2 teaspoons of baking powder, and ½ teaspoon of kosher salt until well combined.

In a separate bowl, cream together ½ cup of softened unsalted butter, the zest of one lemon, and 1 cup of sugar using an electric mixer until fluffy and pale.

Gradually add in the dry flour mixture to the creamed butter, alternating with ¾ cup of buttermilk, until just combined.

Gently fold the prepared blueberries into the batter using a spatula.

Pour the batter into a greased 8- or 9-inch baking pan. Sprinkle a tablespoon of sugar evenly over the surface. Bake in a preheated oven at 350°F for 35-45 minutes.

Once baked, remove the cake from the oven and let it cool in the pan for 15 minutes before transferring it onto a wire rack to cool completely.