Whisk until smooth and fluffy, approximately 2 minutes. • Add eggs, vanilla, lemon zest, and buttermilk. Whisk until smooth, and add flour, baking powder, soda water, and salt. Mix until just combined. Stir in blueberries. Batter will be thick. • Spoon batter into a large disposable piping bag or freezer bag (or spoon batter into the pan).