Preheat oven to 425.
Spray a 12"x17" sheet pan with non stick cooking spray and line with parchment paper, set aside.
In a large bowl whisk together buttermilk, eggs, vanilla and butter.
In another bowl whisk together flour, sugar, baking powder, baking soda and salt.
Mix your dry ingredients into your wet ingredients until combined.
Fold in your blueberries and lemon zest until distributed.
Pour into prepared pan and spread to sides.
Bake in oven for 13-15 minutes until puffy and golden.
Remove from oven and cut into squares.
Drizzle with syrup and sprinkle with lemon zest if desired.