Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy using an electric mixer or a whisk.
Add the eggs one at a time, mixing well after each addition.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk. Start and end with the flour mixture.
Mix in the lemon zest and lemon juice until fully incorporated.
Gently fold in the blueberries using a rubber spatula, being careful not to break them.
Pour the batter into the prepared cake pan and smooth the top. Bake in the preheated oven for 30 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for 10 minutes. Then transfer it to a cooling rack to cool completely.
While the cake cools, prepare the glaze by whisking together the powdered sugar, lemon juice, and milk in a small saucepan over low heat. Stir until smooth and slightly warm.
Once the cake is completely cool, drizzle the glaze over the top. Allow the glaze to set before serving.