Preheat oven to 350 degrees F (175 degrees C).

Grease a rimmed baking sheet.

In a large bowl, beat eggs with an electric mixer until foamy.

Mix in sugar, oil, vanilla sugar, lemon juice, lemon zest, and salt until well combined.

In a separate bowl, combine flour, baking powder, and cinnamon.

Gradually add the dry ingredients to the wet ingredients, alternating with milk, until the batter is well blended.

Spread the batter evenly onto the prepared baking sheet.

Distribute the blueberries evenly on top of the batter.

Lightly press the blueberries into the batter.

Bake in the preheated oven for 20 to 30 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool completely on the baking sheet, for about 1 to 2 hours.

Dust the cooled cake with confectioners' sugar.

Cut the cake into squares and serve.