Preheat oven to 350 degrees F. Spray a 9-inch round glass pie pan or 8-inch square glass baking dish with nonstick spray.

Place the blueberries in the bottom of the prepared baking dish.

Combine the flour, baking powder, and salt in a small bowl. Combine separately the buttermilk, eggs, sugar, lemon extract, and vanilla extract. Add the wet team and dry team together and stir until smooth. Carefully pour over the blueberries in the baking dish.

Bake in the preheated oven until set, about 30 minutes. Sprinkle with a thin layer of brown sugar (start with 1 tbsp). Return to the oven and bake until the sugar is lightly browned, 10-15 minutes. Serve warm or cold.