In a medium bowl, mix together flour, 1/4 cup sugar, baking soda, and cream of tartar. Stir in ginger and lemon zest.
In a small bowl, combine buttermilk and oil and add to the dry ingredients, stirring just until blended. Turn the slightly sticky dough out onto a lightly floured work surface and pat to 1/2-inch thickness. Using a floured, 4-inch round cutter, cut out the dough.
Cut each circle in half to make half-moons. Re-roll and cut the scraps, handling the dough as little as possible. Place scones onto a baking sheet that has been lightly coated with nonstick cooking spray.
In a small bowl, lightly beat the egg with the water. Brush the tops of the scones with the egg glaze. Sprinkle scones with 1 Tbsp of sugar.
Bake for 15 to 20 minutes, or until the tops are golden and firm to touch. Serve warm.