1) Preheat the oven to 375 degrees. Line a muffin pan with muffin cups or grease with cooking spray. In a large bowl whisk the flour, sugar, lemon zest, baking powder, baking soda, and salt. Set aside.
2) In a medium bowl whisk the melted butter, eggs, buttermilk, and vanilla. Pour wet ingredients into dry and gently mix until just combined. Batter will be slightly lumpy. Fold in the blueberries. Scoop into muffin tin and bake for 18-20 minutes. Remove from oven and generously sprinkle the Cassonade Sugar on top!
*Make sure all your ingredients are at room temperature.