In a large bowl whisk together the flour, salt, baking powder, sugar, and lemon zest.
Add the cold diced butter and using your fingertips, rub the butter into the flour mixture until it resembles coarse crumbs.
Create a small well in the center of the flour mixture. Pour the heavy cream and vanilla into the well and stir with a fork until the dough comes together.
Toss in the blueberries and mix gently with your hands to combine.
Turn the dough out onto a floured surface. Form into an 8-inch disk, cover with plastic wrap, and refrigerate for 30 minutes.
After 30 minutes, cut into 8 wedges with a sharp knife.
Transfer to a parchment-lined cookie sheet and pop your tray into your fridge for 15 minutes.
Preheat oven to 400º F (200º C).
Brush the scones with heavy cream and bake for about 18 to 20 minutes or until risen and golden brown. Remove from oven and allow to cool down a little before serving.
Prepare the glaze: Mix the ingredients in a small bowl until smooth.
Drizzle glaze over scones and serve.