Step 1

Preheat the oven to 400 degrees F. Line 2 baking sheets with parchment paper.In a mixing bowl, combine the flour, sugar, baking powder, and salt. Add the butter and toss with the flour. Add the egg, buttermilk and vanilla. Mix until just combined, being careful not to overmix. Fold in the blueberries and lemon zest.Turn the dough onto a floured surface and then pat into 1-inch-thick square. Cut the dough into 2 inch squares. Place pieces, about 2 inches apart on the prepared baking sheets. Brush each piece with buttermilk.Bake until golden brown, 15 to 18 minutes, rotating sheets halfway through. Let the scones cool slightly and then drizzle with the lemon poppy seed glaze (see below). Serve warm with butter.

Step 2

In a bowl, whisk together the powdered sugar, butter, lemon juice, and vanilla, adding water if needed to thin slightly or more sugar if needed to thicken. Stir in the zest of 1/2 a lemon and the poppy seeds. Drizzle the glaze over the scones.