Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan or line it with parchment paper.

In a large mixing bowl, cream the softened butter and granulated sugar together using an electric mixer until light and fluffy, about 3-4 minutes.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and lemon zest.

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this dry mixture to the butter mixture, alternating with the milk. Start and end with the flour mixture. Mix until just combined.

Gently fold in the blueberries, being careful not to break them.

Pour the batter into the prepared cake pan and smooth the top with a spatula. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.

While the cake cools, prepare the lemon drizzle by whisking together the powdered sugar, lemon juice, and lemon zest until smooth.

Once the cake is completely cool, pour the lemon drizzle over the top, allowing it to drip down the sides. Slice and serve.