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.
Scatter butter pieces, lemon zest, and poppy seeds over flour mixture and pulse until the butter is incorporated and the mixture resembles sandy crumbs.
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).
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.
Prepare glaze by whisking together powdered sugar, lemon juice, water, and vanilla extract. Glaze is the right consistency when you raise your whisk out of the bowl and it forms a ribbon that holds its shape for several seconds before dissolving back into the bowl. If glaze is too thin, add a bit more powdered sugar, if it is too thick, add a splash more water.
Drizzle glaze over scones or dip the tops of cooled scones into the glaze. Allow glaze to harden (about 15 minutes) before enjoying.
¹When zesting your lemon, be sure to avoid the pith, which is the bright white layer close to the flesh of the lemon.You will also need 1 ½ Tablespoons (20ml) of lemon juice for the scone glaze, so don’t toss your lemon after zesting! It’s easier to zest the lemon first and then squeeze it.