• Adjust the oven rack to the center position and preheat to 400°F. Line two baking pans with parchment paper.
• In a large bowl, whisk together the flour, sugar, lemon zest, salt, baking powder and baking soda.
• Add the butter and cut with a pastry cutter or a fork until the butter is the size of large peas.
• In a measuring glass, whisk together the buttermilk and 1 egg. Make a well in the middle of the flour/butter mixture and add the liquid mixture. Mix until partially combined. Use a spatula to gently fold in the blueberries to the scone dough. Take care not to break the blueberries or their color will bleed. If using frozen blueberries, keep frozen and don’t thaw before using.
• Transfer the dough to a floured surface and divide into 2 equal parts. Gently knead each into 3/4-inch thick, 6-inch diameter rounds. Cut each round into 8 wedges and place on your prepared baking pans. Space them out about 2 inches apart.
• In a small bowl, combine the remaining egg with 1 teaspoon of water. Brush over the scones.
• Bake for 12 to 15 minutes or until lightly browned.

Make the glaze:

• In a small bowl, combine the sugar, crushed and sifted blueberries, and lemon juice with a fork until a smooth and thick glaze forms. Add more powdered sugar to make the glaze thicker or thinner with lemon juice, to your desired consistency. Drizzle or dip each scone with the glaze. Let set before serving. Scones are best served the day they’re baked.