Preheat the oven to 425 degrees F. Line a baking sheet with parchment and set aside.
In a large mixing bowl, add the sugar and blood orange zest. Rub the two together until you can really smell the blood orange zest and it’s evenly distributed throughout the sugar. Whisk in the all-purpose flour, poppy seeds, baking soda and salt.
Using a box grater, grate the butter into the dry ingredients and mix quickly, breaking up the butter so it’s broken up into pea-sized bits throughout.
Create a well in the center of the flour mixture and pour in the buttermilk. Using a wooden spoon, mix it together until it forms a shaggy ball. Drop the dough onto a lightly floured counter and knead a few times, being sure to not over handle it, which will result in tough scones. Form the dough into 1 1/2-inch- thick disc. Using a knife, cut the scones into 6 equal triangles. Transfer the scones to the baking sheet and put in the freezer to chill for 15 minutes.
Brush the tops with buttermilk and transfer the scones to the oven and bake for 25 to 30 minutes, until a skewer inserted into the centers comes out clean and the scones are golden brown.
While the scones are baking, make the glaze. In a small bowl, whisk the powdered sugar with the juice from the one blood orange. Since all blood oranges are a different size (I got about 1 tablespoon of blood orange juice) you may need to add a bit more juice or a splash of milk to get it to the right texture.