Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a large bowl, whisk together flour, baking powder, baking soda, and salt.

In a separate bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in lemon extract.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.

Gently fold in the blueberries.

Pour batter into the prepared pan and bake for 25-30 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.

In a medium bowl, whisk together powdered sugar, lemon juice, and lemon zest until smooth.

Drizzle the glaze over the cooled cake.