Preheat oven to 400°F.

In a medium bowl, combine sugar and lemon zest. Using your fingertips, mix together. Stir in flour, baking powder, baking soda, and salt.

Using largest holes on a box grater, grate partially frozen or very cold butter. Add to flour mixture and mix until it resembles coarse meal.

In a small bowl, combine egg and cream and mix well. Pour into flour mixture. Mix well, scraping down the sides of the bowl. Scrape dough out onto a lightly floured surface. Using hands, shape dough into a ball, making sure to fold in all the loose clumps.

Shape into a 7 inch circle, approximately 3/4 inch thick, and cut into 8 equal pieces. With space between each triangle, place on a parchment paper covered prepared baking sheet. (Alternatively, you can use a scone pan.) Bake for approximately 15 minutes, or until golden brown. Allow scones to cool to room temperature on a wire rack and prepare glaze.

In a small bowl, combine all of the glaze ingredients and whisk until smooth. Drizzle glaze over cooled tops of the scones and allow glaze to harden. (Alternately, brush scones with the glaze.)