In a mixing bowl, combine the blueberries, granulated sugar, lemon zest, lemon juice, cornstarch, and vanilla extract. Gently mix until the blueberries are coated. Set aside.

In another bowl, cream together the softened butter and powdered sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the baking powder and salt.

Gradually add the flour, mixing until just combined.

Preheat the oven to 350°F (175°C). Grease a baking dish.

Spread half of the soufra base mixture in the bottom of the prepared baking dish.

Pour the blueberry filling over the base, then dollop the remaining soufra mixture on top.

Bake for 30 minutes or until golden brown and set. Let cool before serving.