Pre-heat oven to 200C. Mix your dry ingredients together. Sieve flour with baking powder, sugar and salt.
Rub the cold butter or use a food processor to pulse the butter into the dry ingredients until you have a sandy mixture. Turn it out into a huge, deep bowl.
Add the lemon zest, juice and dried cranberries. Mix with your hands. Slowly pour in the buttermilk a little at a time while working the mixture into a mouldable dough. It shouldn't be too sticky but not too dry either.
Tip it out onto a floured surface. Do not knead it anymore at this point. Just shape it out to about an inch flat.
Use cutters to cut out the scones. I used quite a small one (about 5cm).
Lay them on a lined tray. Brush tops with beaten egg and sprinkle the sugar over them to give it that crunchy exterior.
Bake for 15 to 20 mins. Eat while they're warm.