Preheat oven to 375F (190C) and line a baking sheet with parchment paper. Set aside.
In the basin of a food processor, combine flour, sugar, baking powder, and salt. Pulse to combine.
2 cups (250 g) all-purpose flour,⅓ cup (70 g) granulated sugar,1 ¼ teaspoon baking powder,¼ teaspoon salt
Scatter butter pieces, lemon zest, and poppy seeds over flour mixture and pulse until the butter is incorporated and the mixture resembles sandy crumbs.
½ cup (113 g) very cold unsalted butter,1 Tablespoon poppy seeds,1 ½ Tablespoons fresh lemon zest¹
Combine heavy cream and vanilla extract in measuring cup and then drizzle over the mixture in the food processor. Pulse until dough is beginning to clump together (see photo in post for visual).
½ cup (120 ml) heavy cream,¼ teaspoon vanilla extract
Transfer dough to a lightly floured surface and fold the dough in half and use your hands to gently flatten layers together. Rotate the dough 90 degrees and fold in half again, repeating this step several times while being careful to not overwork the dough.
Gently form dough into a 6” disc and cut into 8 even wedges (press straight down with the knife, don’t saw into the dough, this will help keep your scones from falling over in the oven).
Transfer to prepared baking sheet and transfer to 375F (190C) preheated oven. Bake for 15-17 minutes or until edges are beginning to turn golden. Allow to cool completely on baking sheet before covering with glaze.