Preheat the oven to 400 degrees F. Line 2 sheet pans with parchment paper.
In a large bowl, stir together 3 cups all-purpose flour, baking powder, granulated sugar, salt and lemon zest.
Use a fork or pastry blender to cut the butter into the dry ingredients, until it resembles pea-sized clumps. You can also rub the butter and flour together with your fingers.
In a small bowl, whisk together the egg, milk and vanilla extract. Stir into the flour-butter mixture. The dough will turn into clumps.
Before the dough is fully combined, toss the blueberries in 1 tablespoon flour in a small bowl, and then add them to the dough, gently pressing it together.
Drop the dough by 1/4 to 1/3-cup-full in mounds on the sheet pans spreading 3 inches apart. It is easy to do this with a cookie scoop.
Brush the tops with milk and sprinkle with coarse sugar.
Bake until golden brown, about 18-20 minutes.
Cool the scones on a wire rack.