Preheat oven to 400°F. Line a baking sheet with parchment paper.

Combine flour, salt, baking powder and baking soda in a large bowl and set aside.

Add the butter to your flour mixture and cut the butter cubes with a pastry cutter (or your fingers) until they're pea sized pieces.

In a small bowl combine your sugar, thyme, and lemon zest and mix. Transfer to food processor, spice grinder, or mortar and pestal and grind into a fine sugar powder.

Pour in your buttermilk and sugar mixture. Stir until a thick dough forms, and then use your hands to combine until dough is crumbly, but easy to manage.

Place your dough onto your parchment lined baking sheet, pat into an 8-inch circle, and cut into 8 wedges with a sharp knife. Brush with your 2 tablespoons buttermilk. Arrange the wedges around the baking sheet, leaving room for rising and expansion while they bake.

Bake for 18-20 minutes, or until golden brown. Cool on a wire rack. Make your icing while your scones bake.

For the icing: Add the powdered sugar, lemon juice, and vanilla extract to a small bowl and stir until combined. Drizzle over scones after scones have cooled for a few minutes.