Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan or line it with parchment paper.
In a large mixing bowl, cream together the softened butter and granulated sugar using an electric mixer or whisk until light and fluffy, about 3-5 minutes.
Add in the eggs one at a time, mixing well after each addition. Then stir in the lemon zest and lemon juice until well combined.
In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, alternating with the milk. Begin and end with the flour mixture. Mix until just combined; do not overmix.
Gently fold in the fresh blueberries using a rubber spatula, being careful not to break them.
Pour the batter into the prepared baking pan and smooth the top. Bake in the preheated oven for 35-40 minutes or until a toothpick inserted in the center comes out clean.
Once baked, remove the cake from the oven and allow it to cool in the pan for about 10 minutes. Then transfer it to a cooling rack to cool completely.
Once cooled, you may dust the top with powdered sugar if desired, slice, and serve.