1 Make the dough in a food processor: Measure the flour, sugar, baking powder, baking soda, and salt into a food processor. Process the ingredients to combine them evenly.
Sprinkle the cubed butter over the flour mixture, and process the mixture in 1-second pulses until the butter is no longer visible and the mixture looks somewhat sandy.
In another mixing bowl, whisk together the yogurt and egg until no streaks of egg yolk remain. Pour this mixture into the food processor with the flour and the butter.
Run the food processor for about three seconds, just until all of the flour is absorbed and the dough begins to come away from the sides of the bowl.
2 Fold in the blueberries: Turn out the dough onto a lightly floured surface. Scatter the blueberries over top and fold the dough a few times with a spatula to incorporate. (You can also do this in a separate mixing bowl instead of on the counter, if you prefer.)
3 Shape the dough into disks and chill: With a bench scraper or knife, divide the dough in half and pat into two disks, about 1/2-inch thick and six inches across (you can use the length of your hand as a guide).
Wrap the disks of dough in plastic wrap and refrigerate for at least two hours, or up to 24 hours.
4 Preheat the oven to 350F: Line a baking sheet with a silicon baking mat or parchment paper.
5 Cut and bake the scones: Unwrap the disks of chilled dough and cut each one into eight wedges (16 wedges total).
Place the wedges an inch apart on the lined baking sheet. Try not to touch the sides or handle the scones too much as you transfer them since this can inhibit how much they rise in the oven.
Bake the scones for 15 to 18 minutes, until they are lightly browned.
6 Make the glaze: While the scones are baking, whisk together the lemon zest, lemon juice, and powdered sugar in a small bowl. The glaze should be a pourable consistency; add additional lemon juice (or milk, or water) 1 teaspoon at a time if needed.
7 Glaze and cool the scones: Transfer the scones to a cooling rack with something underneath to catch any dripping glaze (I use wax paper). While the scones are still warm, drizzle each one with a teaspoon of the glaze. Let the scones cool until the glaze has fully set, about 30 minutes.