1. Zest lemon and set aside.
2. Slice the lemon in half. Juice lemon and set aside the juice.
3. In a large mixing bowl, stir together flour, sugar, baking powder, baking soda and salt and lemon zest.
4. Using pastry blender (or by hand) cut in butter until mxture is crumbly.
5. Add buttermilk and stir with a fork to make a soft, sticky dough.
6. Lightly flour hands and press dough into a ball.
7. On a lightly floured surface, knead 10 times.
8. Carefully, fold in the blueberries.
9. Press dough until it is 1" thick. (don't worry about the shape here)
10. Using a 2-1/2 inch cutter, cut out rounds.
11. Place on ungreased baking sheet.
12. Scraps can be gathered up and repeated to cut out more rounds.
13. Brush tops of scones with beaten egg mixture.
14. Bake in 425°F oven for 12 to 15 minutes or until golden.
15. For lemon glaze, mix 1 cup of powdered sugar with 2 tbsp of lemon juice and 1-1/2 tsp lemon zest. Add more lemon juice until desired consistency. Drizzle over top of scones.