Kue Sarapan Blueberry Buttermilk

Bahan-bahan (6 porsi)

• 1/2 cup unsalted butter (softened)
• zest from one lemon
• 1/2 cup sugar
• 1 egg
• 1 teaspoon vanilla
• 2 cups flour (divided )
• 1 teaspoon salt
• 2 teaspoons baking powder
• 2 cups fresh blueberries
• 1/2 cup buttermilk
• 1 tablespoon coarse sugar (for topping )