Preheat the oven to 350°F (175°C) and grease a 9-inch round cake pan.
In a mixing bowl, beat the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes using an electric mixer.
Add the eggs, one at a time, mixing well after each addition. Then stir in the vanilla extract and lemon juice.
In another bowl, whisk together the flour, baking powder, salt, and dried lavender.
Gradually add the dry ingredients to the wet mixture, alternating with the milk, starting and ending with the flour mixture. Mix until just combined, do not overmix.
Gently fold in the fresh blueberries, being careful not to crush them.
Pour the batter into the prepared cake pan and smooth the top with a spatula.
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.
Optional: Dust the cooled cake with powdered sugar before serving.