Preheat the oven to 400 degrees with the racks in the lower and upper thirds of the oven.

Using a stand mixer (or large bowl) beat together with a paddle attachment on low the flour, granulated sugar, baking powder, and salt. Slowly begin adding the bite sizes pieces of butter to the blender and beat on low until the flour mixture resembles coarse meal, with a few pea-size pieces of butter remaining. Add ½ cup buttermilk, orange zest, juice, egg yolk, and poppy seeds until just combined in the mixer. *Do not over mix.

On a lightly floured surface turn out the dough and knead several times on the floured surface. Form the dough into a 7-inch square; cut into 9 squares, then cut each in half diagonally. Transfer the dough triangles to two parchment-lined rimmed baking sheets. Brush the tops with the remaining 2 tablespoons of buttermilk and sprinkle with coarse sugar. Bake until scones are pale golden in color about 15-17 minutes (rotating the baking sheet half way through if you do not have a convection oven). Let the scones cool on wire racks and serve with butter and jam if desired.