In a large mixing bowl, combine the sugar and lemon zest. Rub them together with your fingers or a spoon until the mixture feels like coarse, fragrant sand.
½ cup sugar, 2 lemons
Whisk in the flour, baking powder, and salt.
2 cups all-purpose flour, 2 ½ teaspoons baking powder, ½ teaspoon salt
Grate or chop the cold butter and add it to the flour mixture. Use a pastry cutter or fork to blend it in until the mix resembles coarse crumbs with a few larger pieces.
8 tablespoons unsalted butter
In a separate bowl, combine the egg, heavy cream, lemon juice, and vanilla extract. Whisk until smooth.
1 large egg, ½ cup cold heavy cream, 2 tablespoons lemon juice, 2 teaspoons vanilla extract
Make a well in the center of the dry mixture. Pour in half of the wet ingredients and gently stir. Add the rest and mix just until the dough begins to come together—it should still be a bit shaggy.
Gently fold in the frozen blueberries. Avoid overmixing to keep the scones tender.
1 ¼ cups frozen blueberries
Turn the dough out onto a floured surface. Pat it into a rough ball, then press into an 8-inch disk. Fold it in half once, press it back into a disk, and neaten the edges.
Transfer the dough disk to a parchment-lined baking sheet or plate and freeze for 30–40 minutes. Meanwhile, preheat the oven to 400°F (200°C).
Slice the chilled dough into 6–8 wedges. Arrange them 2 inches apart on a lined baking sheet. Brush the tops with a bit of heavy cream.
Bake for 18–22 minutes or until golden and lightly crisped. Let cool slightly on the baking sheet, then transfer to a wire rack.
Stir together the powdered sugar and lemon juice until smooth.
1 cup powdered sugar, 2-3 tablespoons lemon juice
Drizzle over the cooled scones and let them set before serving.