Preheat the oven to 180°C (350°F) and grease a cake pan.
In a bowl, beat the butter and sugar until light and creamy.
Add the eggs one at a time and mix well.
Stir in the lemon juice and mix until combined.
In another bowl, mix flour and baking powder.
Gradually add the dry ingredients to the wet mixture and mix gently.
Fold in the blueberries carefully.
Pour the batter into the prepared cake pan.
Bake for 30–35 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool before slicing and serving.