Preheat the oven to 400°F (200°C) with a rack set in the middle position. Line a cookie sheet with parchment paper. Set aside.

In the mixing bowl of the stand mixer fitted with the flat beater attachment, beat flour, granulated sugar, lemon zest, baking powder, and salt on low (1–2) speed until blended. Add butter and continue beating until coarse crumbs are formed. 

In a small bowl, whisk together ¾ cup (180 milliliters) cream, egg, and vanilla extract. Add to the flour mixture and continue beating until the dough starts to come together. 

Turn the dough out onto a lightly floured surface and pat into a 6-by-8-inch (15-by-20-centimeter) rectangle. Evenly top one half of the dough with ½ cup (85 grams) blueberries; fold the dough in half to cover blueberries. Pat again to a 6-by-8-inch (15-by-20-centimeter) rectangle, top one half of the dough with remaining ½ cup (85 grams) blueberries, and fold in half to cover the blueberries. Seal the edges to enclose the berries and gently pat the dough into a 6-inch (15-centimeter) disk. Cut the dough into 6 wedges. Place the wedges on the prepared cookie sheet. 

Brush the top of the scones with remaining 1 tablespoon (15 milliliters) heavy cream and sprinkle with coarse sugar (if using). 

Bake until golden brown, 20–24 minutes.

Variations:

Orange Cranberry Scones
Follow step 1. In step 2, substitute 1½ tablespoons (9 grams) grated orange zest for the lemon zest and add 1 cup (128 grams) dried cranberries after mixing in butter. Omit blueberries in step 4. Continue as directed.

Chocolate Chip Scones
Follow step 1. In step 2, omit lemon zest, reduce granulated sugar to 2 tablespoons (24 grams), and add 2 tablespoons (28 grams) packed brown sugar. Add 1 cup (170 grams) semisweet chocolate chips after mixing in butter. Omit blueberries in step 4. Continue as directed.