Adjust your oven rack to lower-middle position and preheat oven to 400°F. Line a baking sheet with parchment paper.

In a large bowl, combine sugar and Orange zest; mixing with your fingertips until the sugar is moistened and fragrant. In a separate bowl whisk together the flour, baking powder, baking soda, and salt. Then add this to the moistened sugar and mix until combined.

Grate frozen butter into flour mixture on the large holes of a box greater; use your fingers to work in the butter until the mixture resembles coarse meal.

In a small bowl, whisk the sour cream and egg until smooth.

Using a fork, stir in sour cream mixture into flour mixture until large dough clumps form. Use your hands to press dough against the bowl into a ball. The dough will be sticky at first, but as you keep pressing, the dough will come together. Just be careful not to overwork the dough.

Place dough on a lightly floured surface and pat into a 7 in circle about 3/4 inch thick. Use a sharp knife to cut into 8 triangles; place on a prepared baking sheet, about 1 inch apart. Bake until golden, about 15-17 minutes. Cool for 10 minutes and prepare the glaze.

In a medium bowl, prepare the glaze by mixing together the melted butter, confectioners sugar, vanilla and Orange juice. Whisk until smooth. Dip the top of the scones into the glaze and allow the glaze to harden. You can either leave them as is or double dip them. When I made dipped mine once it left a thick glaze on top so I didn't have to double dip mine.

These scones store well in an airtight container for up to 2 days.