First, make the base dough: cream the butter, granulated sugar and lemon zest until reaching an ointment texture. Then add the flour and beat until everything is well mixed. Let the dough set for 20 minutes, covered.
Once the resting time is over, put the dough in a buttered 10×14-inch mold and distribute, pressing with your fingers.
Bake in a preheated oven at 320°F for 15 to 18 minutes. Take out and allow to cool.
For the filling, mix the eggs and sugar with a whisk in a bowl. Then add the sifted flour and mix everything together. Lastly, add lemon juice and mix well.
Distribute the filling over the baked dough, scatter blueberries across the surface and put in the oven for 30 more minutes at 320°F, or until it looks brown and set.
Allow to cool completely before cutting into squares.
Sprinkle some powdered sugar on top before serving.