Preheat the oven to 400 F degrees.
In a large bowl combine the flour, sugar, baking powder, salt and lemon zest. Whisk to combine everything.
In a small bowl whisk the egg yolk, buttermilk and vanilla extract together.
Add the butter to the flour bowl, and using a pastry blender, cut in the butter to make small pea sized pieces.
Add the buttermilk mixture to the flour mixture and stir until the dough pulls together. Lightly flour a work surface and dust your hands with flour.
Transfer the dough to the work surface and knead it gently about 5 time. Shape the dough into a ball, then flatten it into a disk that's about 3/4 of an inch thick and about 8 inches in diameter.
Cut the disk into 8 wedges of equal size. Place the wedges onto a baking sheet.
Bake them for about 20 minutes or until golden. Transfer the scones to a cooling rack.
To make the lemon glaze, add the confectioners' sugar to a bowl. Add the corn syrup, milk, lemon juice, pinch of salt and start whisking until smooth. Add more milk until the glaze is runny but still thick.
While the scones are cooling drizzle them generously with the glaze then garnish with more lemon zest.