Preheat oven to 400°. Line a rimmed baking sheet with parchment paper.
In a large bowl, whisk together flour and 2 tablespoons granulated sugar. Add grated butter, stirring to combine. Add ½ cup buttermilk and gently stir to combine.
Turn dough onto a lightly floured surface; gently knead dough until it comes together, 5 or 6 times. Roll dough to ½-inch thickness. Using a 3-inch round fluted cutter dipped in flour, cut dough without twisting cutter, into 6 rounds, rerolling scraps once. Place shortcakes 2 inches apart on prepared baking sheet.
In a small bowl, whisk together remaining 1 tablespoon buttermilk and egg. Brush on tops of shortcakes. Sprinkle with turbinado sugar.
Bake until golden brown, 12 to 14 minutes. Let cool.
In a small bowl, whisk together cream and 2 tablespoons granulated sugar. Whisk, vigorously, until soft peaks form. Fold in crème fraîche.
In another small bowl, stir together blueberries, remaining 2 tablespoons granulated sugar, lemon zest and juice, and salt.
Split shortcakes. Spoon whipped cream and blueberry mixture onto shortcakes. Garnish with lemon zest, if desired.